I start a new game and it sits at around 5MB, but after a few hours of saving my saves already weigh about 27MB; this has been going on for a while, though, and I've lost saves that sat upwards of 50MBs before starting over. I've tried reinstalling the game and all of my mods; I'm pretty sure one of the mods I have recently installed is causing it, but I have no idea which one. If there's anything to be found in my load order, I'll post it. Erstwhile, I'll go through and clean everything with TESVEdit and start checking off mods one by one until I find the culprit.
This happens with a new game, so it isn't from anything leftover from an uninstalled mod.
My load order:
? 01 Update.esm
? 02 Unofficial Skyrim Patch.esp [Version 2.0.0]
? 03 Dawnguard.esm
? 04 Unofficial Dawnguard Patch.esp [Version 2.0.0]
? 05 HearthFires.esm
? 06 Unofficial Hearthfire Patch.esp [Version 2.0.0]
? 07 Dragonborn.esm
? 08 Unofficial Dragonborn Patch.esp [Version 2.0.0]
? 09 Falskaar.esm
? 0A SPIKE.esm
? 0B Brawl Bugs CE.esp
? 0C HearthFire Display Case Fix.esp
? 0D Krill_AurielsBowFix_20BaseDamage.esp
? 0E AOS.esp
? 0F QuieterRestorationDrawnSound.esp
? 10 StaticMeshImprovementMod.esp
? 11 StaticMeshImprovementMod-DragonbornTernFix.esp
? 12 ClamsDropPearls.esp
? 13 UnlimitedBookshelves.esp
? 14 Marco's Integrated Leveled Lists.esp
? 15 marriagedynamicoutfits.esp
? 16 ShootingStars.esp
? 17 Unique BOOZE Bottles.esp
? 18 AMatterOfTime.esp [Version 1.00]
? 19 SkyUI.esp
? 1A Lore Weapon Expansion.esp [Version 1.0]
? 1B Lore Weapon Expansion - Goldbrand.esp [Version 1.1]
? 1C ERSO 09 - Vendor Trainer Quest-giver protected USKP.esp
? 1D ERSO 09.1 - Essential Children.esp
? 1E ERSO 30 - Better Enemy AI Dawnguard&Dragonborn.esp
? 1F ERSO 30.1 - Better Expert Level.esp
? 20 BHTNF.esp
? 21 more plants all.esp
? 22 Nightingale Hall.esp
? 23 A&P weight change only..esp
? 24 BardRequestBreak.esp
? 25 Book Covers Skyrim.esp
? 26 Book Covers Dawnguard.esp
? 27 Book Covers Hearthfire.esp
? 28 Book Covers Dragonborn.esp
? 29 Guard Dialogue Overhaul.esp
? 2A HFFF.esp
? 2B NeutralHjerim.esp
? 2C NoLeveledItemRewards.esp
? 2D TimingIsEverything.esp
? 2E Realistic Lighting Overhaul - Dawnguard Interiors.esp
? 2F Realistic Lighting Overhaul - Major City Exteriors.esp
? 30 Realistic Lighting Overhaul - Major City Interiors.esp
? 31 Realistic Lighting Overhaul - Minor Cities and Town Interiors.esp
? 32 RLO - Adaptive Interiors Vanilla Weathers Patch.esp
? 33 PTAlchemyFoodOverhaul.esp
? 34 The Dance of Death - Ultimate Edition.esp
? 35 Alteration and Restoration redux.esp
? 36 dD-No Spinning Death Animation.esp
? 37 Skyrim Unbound.esp
? 38 ethereal_elven_overhaul.esp
? ++ Better Summoning Visuals - TheGreyLight.esp
? 39 WATER.esp
? 3A WATER DG.esp
? 3B WATER DB Waves.esp
? 3C WATER Falskaar.esp
? 3D Alternate Hearthfire House Map Marker Optional Version 2.esp
? 3E PTAlchemyOverhaul_SkillRate_1_0.esp
? 3F Bashed Patch, 0.esp
? 40 VHTNF.esp
? 41 proudspiremanortnf.esp
? 42 HSTNF.esp
? 43 hjerimtnf.esp
? 44 Realistic Lighting Overhaul - Brighter Dungeons.esp
If it helps, I'm also running HiAlgoBoost. I don't see how that could be causing any issues with my saves, though, if I'm right in assuming bloat is caused by errant scripts.