How do I limit the amount of new health the creatures gain everytime a new level is reached? I'm getting sick of the fact that by the time I reach level 5, my weapons are only taking a pixel away from their health bar. Also trying to make it so that the monsters don't 1-shot my followers too often.

Or if that's not possible; how do I decrease the amount of inflicted damage that they gain per level perhaps? So that they don't grow stronger too fast.

What mods are you using? That is not my experience of the vanilla game at all. Please post your load order.

Creatures can be set as either offset to the player's level, or have a static level. The first type of creatures are the ones that are likely giving you that kind of problem, but they are certainly not a problem at level 5 since few to none appear at such levels, and most overhauls will put some control measures on the ones that are offset, and generally make the ones that aren't harder to beat, so you have to pick your fights more carefully.

That said, here's how it works:
A static level creature has all of its stats individually set in its creature's entry. It always has the same health and attack damage that the editor gave it, regardless of your level. Regular Minotaurs for example are level 12 creatures with 300 HP and 30pts of attack damage, they can cause some trouble to low level characters if they happen to run into one, which using vanilla leveled lists is very unlikely.
A PC level offset creature has a level equal to that of the player's level plus the offset used, which can be positive or negative. Its level is contained between a minimum and maximum amount, which can be uncapped if 0. The creature has a health amount equal to that given to it in the editor x its level, hence its not displayed as 'Health' but as 'Health mult', and can get out of whack easily if it's too high, same thing with fatigue and magicka. Its attack damage is equal to that given to it in the editor + (its level x the game setting fCreatureCalcDamage). This setting defaults to 1, so the creature deals 1 additional pt of damage per level.
Minotaur Lords for example are PC level offset, with an offset of 0, a minimum of 16 and a max of 0. The ones the player encounters are always at least level 16, and scale to always have the same level than the player after you reach level 16. Their health mult is 22, so they always have at least 22 x 16 = 352 HP, and their base attack is 24, so they always deal at least 24 + 16 = 40pts of damage.

EDIT: a creature's attack damage is only used for its unarmed attacks. Creatures that wield weapons use the regular weapon damage formulas that humanoids also use, they use the Combat Skill stat to determine their base Blade, Blunt and Marksman skill values. Their base Strength (for melee), Agility (for bows) and Luck are always static set, but offset creatures get a bonus to all combat skills equal to their level x fCreatureCalcCombat setting, which defaults to 2.

If you feel a particular creature is more overpowered than it should be due to this, you'll have to change its stats in the editor to suit your tastes. Again, note that most overhauls already do this, but they do it according to the author's tastes. Plus if you change the creature's level or level offsets, you'll have to use Wrye Bash's update NPC levels feature in your savegame if you had already encountered at least one instance of that creature.

http://www.gamesas.com/user/568521-gothemasticator/ I'm not using any mods. Vanilla game right here. I'm about to make one because I'm tired of getting my ass kicked.

http://www.gamesas.com/user/399290-migck/ Thank you for the detailed information. This will be very helpful as I stumble around the CS.