Before I explain, here are my mods and load order:

Skyrim.esm ActiveUpdate.esm Active    Bash Tag suggestion(s): {{BASH: Delev, Relev}}Dawnguard.esm Active    Bash Tag suggestion(s): {{BASH: Delev, Relev}}HearthFires.esm ActiveDragonborn.esm ActiveJSwords.esm Active    Warning: This file contains unexpected (or out of order) records and should be removed.Omegared99-Compilation.esm ActiveSPIKE.esm ActiveHighResTexturePack01.esp ActiveHighResTexturePack02.esp ActiveHighResTexturePack03.esp ActiveUnofficial Skyrim Patch.esp Active    Bash Tag suggestion(s): {{BASH: Delev, Relev}}Unofficial Dawnguard Patch.esp Active    Bash Tag suggestion(s): {{BASH: Delev, Relev}}Unofficial Hearthfire Patch.esp ActiveUnofficial Dragonborn Patch.esp Active    Bash Tag suggestion(s): {{BASH: Delev}}chesko_frostfall.esp Activemorerain.espbetter dynamic snow.esp ActiveImproved Combat Sounds v2.2.esp Activenewheavyarmorsound.esp Activestaticmeshimprovementmod.esp Active83Willows_101BUGS_V4_HighRes.esp Active    Bash Tag suggestion(s): {{BASH: Delev, Relev}}adura_skyrimmerchantmod.esp Activealchemysatchels.esp ActivePrometheus_BeastSkeletons.esp Activebirdshf.esp Active    Note: Obsolete. Update to latest version, BirdsHFclean.esp.chesko_wearablelantern.esp Activefishinginskyrim.esp Activehere there be monsters.esp Activehigherlevelenemies.esp Active    Bash Tag suggestion(s): {{BASH: Relev}}unlimitedbookshelves.esp Activenew guards.esp Activesmeltorswheretheyshouldbe.esp Activeunderwater_treasure.esp Activevibrantauroras.esp ActiveConvenient Horses.esp Activechesko_lorebasedloadingscreens.esp ActiveDYNAVISION Dynamic Depth of Field.esp Active    Note: Make sure you have not switched DoF off in your ini file. If you don't see any effect, open you Skyrimprefs.ini and look for 'bDoDepthOfField'. Make sure it is set to 1.wetandcold.esp Activeskyui.esp ActiveiHUD.esp ActiveBosmerArmorMATY743.esp Active    Bash Tag suggestion(s): {{BASH: Relev}}Cloaks.esp ActiveCloaks - Dawnguard.esp ActiveDragonbornArmorFix.esp Activedragonboneweaponscomplete.esp Activedragonhiderobearmor.esp ActiveEinherjarArmor.esp Activehothtrooper44_ArmorCompilation.esp Active    Contains dirty edits: 7 ITM, 0 UDR records. Needs TES5Edit cleaning. A cleaning guide is available here.    Bash Tag suggestion(s): {{BASH: Delev, Relev}}isilnarsil.esp Active    Contains dirty edits: 17 ITM, 0 UDR records. Needs TES5Edit cleaning. A cleaning guide is available here.nordicrangerarmor.esp ActiveNorthborn Fur Hoods.esp ActiveOmegared99-WeaponSets.esp Activeredguardknight.esp Activesamuraiarmor.esp Activethrowingweapons.esp Activevagabondarmor.esp Activevanguardarmor.esp Activewarchiefarmor.esp Activewitchplate.esp Activedr_bandolier.esp ActiveHarvestOverhaulDawnguardDragonborn.esp ActiveSkyRe_Main.esp Active    Bash Tag suggestion(s): {{BASH: Relev, Delev}}    Note: If lockpicking is not work then try to delete 'interface\lockpickingmenu.swf'.    Note: If you have a problem with aiming try to install this mod.    Note: To make aiming easier add the following lines to Skyrim.ini:    Note: [Actor]    Note: fVisibleNavmeshMoveDist=12288.0000    Note: [Combat]    Note: f1PArrowTiltUpAngle=0.64    Note: f3PArrowTiltUpAngle=0.64    Note: fMagnetismStrafeHeadingMult=0.0    Note: fMagnetismLookingMult=0.0SkyRe_Combat.esp ActiveSkyRe_CraftingFix.esp ActiveSkyRe_EncounterZones.esp ActiveSkyRe_EnemyAI.esp ActiveSkyRe_EnemyScaling.esp Active    Bash Tag suggestion(s): {{BASH: Relev}}SkyRe_HarvestOverhaulDawnguardDragonbornPatch.esp ActiveSkyRe_Survivalism.esp ActiveAesirArmor.esp ActiveForgotten Windmill.esp Activehg.esp Activehunting in skyrim - no perks.esp Activequest_pitfighter.esp ActivePumpingIron.esp Activerun for your lives.esp Activethedomain.esp Active    Warning: This file contains 1 deleted NavMesh record that TES5Edit cannot repair automatically and it may cause problems with your game. NavMesh deletions should be reported to the mod author. A guide to repairing NavMesh deletions with TES5Edit is located here.AchieveThat.esp Activealternate sunglare.esp Activefaster vanilla horses.esp ActiveGuard Dialogue Overhaul.esp ActiveImmersive Weapons.esp Active    Bash Tag suggestion(s): {{BASH: Delev}}PalistovSpinningArrows.esp ActivePalistovSpinningArrows_Dawnguard.esp ActivePalistovSpinningArrows_ImmersiveWeapons.esp Activewalk.esp ActiveaMidianborn_Skyforge_Weapons.esp ActiveHelgen Reborn.esp Activeenhanced_bridges.esp Activedetailed outskirts.esp Activesos - the dungeons.esp Active    Note: Do not use the Crash Fix ESP for this mod. It is flagged as a master and is only meant as a last resort for fixing crashes.sos - the wilds.esp Active    Note: Do not use the Crash Fix ESP for this mod. It is flagged as a master and is only meant as a last resort for fixing crashes.sos - civilization.esp Active    Note: Do not use the Crash Fix ESP for this mod. It is flagged as a master and is only meant as a last resort for fixing crashes.Realistic Lighting Overhaul - Dungeons.esp ActiveRealistic Lighting Overhaul - Dawnguard Interiors.esp ActiveRealistic Lighting Overhaul - Major City Exteriors.esp ActiveRealistic Lighting Overhaul - Major City Interiors.esp Active    Warning: Due to conflicts between Sounds of Skyrim - Civilization and Realistic Lighting Overhaul - Major City Interiors.esp it is recommended you use the appropriate compatibility patch found here.Realistic Lighting Overhaul - Minor Cities and Town Interiors.esp Active    Warning: Due to conflicts between Sounds of Skyrim - Civilizaiton and Realistic Lighting Overhaul - Minor Cities and Town Interiors.esp it is recommended you use the appropriate compatibility patch found here.climatesoftamriel.esp Activesaturationboost.esp ActiveSoS - The Dungeons-PatchRLODungeons.esp ActiveSoS - The Dungeons-PatchRLOMajorCityInteriors.esp ActiveRealisticNeedsandDiseases.esp Active    Bash Tag suggestion(s): {{BASH: Delev, Relev}}RND_Dawnguard-Patch.esp ActiveRND_HearthFires-Patch.esp ActiveRND_USKP-Patch.esp Active    Bash Tag suggestion(s): {{BASH: Relev}}RND_Dragonborn-Patch.esp Activemidasskyrim.esp Active    Warning: Original file was released before the Creation Kit (07 Feb. 2012) an update to the previous compatibility patch fixed and cleaned with TES5Edit can be obtained here. (Compatibility Patch)dovahkiinrelax.esp Activenosneakattacksound.esp Activearcherydummyxp.esp Activecrimson tide - blood.esp ActiveUFO - Ultimate Follower Overhaul.esp Active    Note: For safe install need dismiss all your followers, save, delete all included mods, load again, save and install UFO. For safe uninstall or update see special instructions on mod page.UFO - Dawnguard AddOn.esp ActiveUFO - Heartfire AddOn.esp Activereduced distance npc greetings.esp ActiveFollower Trap Safety.esp Activefollowerwander2.esp Active    Note: UFO - Ultimate Follower Overhaul.esp has the same functional, but you can use FollowerWander2.esp on your choice.moveitLWT.esp Activealternate start - live another life.esp Activedd - realistic ragdoll force - realistic.esp Active    Note: Ragdolls will conflict with other mods that change the skeleton.nif. Check Custom Skeleton Replacers for compatibly with other skeleton.nif.SkyRe_Races.esp ActiveTTYM - Think to Yourself Messages.esp ActiveTTYM - Frostfall Module.esp Activepurewaters.esp ActiveRND_PureWaters-Patch.esp ActiveReProccer.esp ActiveReProccerNONPLAYERfix.esp ActiveReProccerDragonborn.esp Active

PC Specs: 4GB DDR3 RAM, Radeon XFX6850 GPU, intel i3 540ghz CPU Other: Latest version of directX and drivers are up to date

Usually, on Skyrim, I dont get FPS lag, inside or outside. And by FPS lag I mean <30 FPS. But now, I get strange lag when the areas dont even seem demanding. For example, Dawnstar, riverwood (a little), Riften, and Whiterun. Sometimes the game just flat out runs slow, with it taking 2 minutes to get into a tavern because of the loading screen and lagging a little there.

I play on high, but change around some settings. i have antialiasing on x4, antistrofic filtering on 12, shadow and radial blur on medium, and the rest are 'high' defaults.

I just find it weird because they happen out of the blue. Really the only mods I use that would affect performance is a character enhancement mod, climates of tamriel, and realistic lighting overhaul.

So does anyone know of some tips and tricks to reduce random lag spikes? Thanks