Some background info: I'm running Skyrim with SKSE and a good 100+ mods (a lot of them are minor fixes) as well as ENB on performance mode, but I've been running it like this for a good few months and no problems.
Not really sure why, but out of nowhere Skyrim started lagging horribly. It began when I neared the end of the Civil War quests, and I've completed the questline (which took forever thanks to the lag) but still experiencing a terrible framerate. I haven't checked exactly what it is, but I wouldn't be surprised if it was less than 7 fps. No mods were suddenly installed to trigger this, nor any changes to my game settings or ENB.
Usually I get around 45fps outdoors and 60 indoors, if that helps. I have no DLC, no CTD's, my saves are around 15mb. I have ENB as an injector, so I tried turning ENB off. It might've changed my lag from 5fps to 6.
I also tried running BOSS, everything seems fine since I've cleaned with TES5Edit before.
Oh, and my GPU and CPU temperatures are on pretty normal temperatures (70c/50c during gameplay, respectively)
Lag seems to not really be dependent on certain areas, it's occuring everywhere in-game: indoors, outdoors, regardless of what map or how many people are in it. The only time lag doesn't hit is during the loading screens (loading takes the average amount of time, too) and during the main menu. It DOES still lag when I pause the game.
Rig Specs: AMD FX-4100 3.6 GHz Quad Core CPU 8GB Patriot 1333mhz DDR3 RAM AMD Radeon HD 7870 2GB GPU Asus m5a78l-m lx Motherboard Some GPU from CoolerMaster, 650W.