Windows 10 feels slow after clean install and thermal paste replacement.

[Tweesieee]

So yesterday I figured that I should replace my thermal paste and do a clean install of Windows 10 because it's been almost 2 years since the last time. I've done it many times before and I know what I'm doing. Everything went smoothly. But after I'd installed all the drivers, I started to notice some change from before. The start-window animation felt off. Like a game that runs @ 30 fps. It worked, but felt "clumsy". I did not care to bother about such a small detail but then I noticed the same could be said about opening windows. The animation was slow, sites loaded slow, even the loading bar for programs had "lag". So I downloaded Fortnite and noticed that I have a lot of stutter in-game even with the lowest settings.
I just figured something had gone wrong with the graphicdrivers, so I removed them and installed them again. Without any success. The issue still remained. So then I did a clean install of Windows again.. aaaaand again. Without any success.
As of writing this, I've done a clean install of Windows 3 times, removed both the graphic card and processor and put them back in again, I've searched all over google but I can't find anything even close to my problem.
So that's why I am here. To ask if any of you have any, if even the slightest clue of why this is happening?

My computer specs is: i7-6700k OC to 4,5GHz, GTX 1080, Corsair 16GB 3000MHz DDR4, Asus z170 Pro Gaming motherboard, Bequiet! 800w psu, 500GB evo SSD and a 1TB HDD.

Thanks!

 

[xtcmax]

Remove OC and report if you see any improvements.

 

[Tweesieee]

Seems like I forgot to mention that I've already tried that. Same results.