computer went slow all of a sudden...

[Zackattack97]

Hi so my computer has been perfectly normal since early this year when I built it my specs on this pc is... NVidia gtx 970, i5 4690k (haven't overclocked yet), PSU evga g2 750w 80+ gold certified, 8gb ram g skill ripjaws, and I have a cpu cooler and a lot of fans... my temperatures are really good so it cant be that... today there was a windows update (windows 10) and I was at school while it happened and when I came back I logged on my computer as usual but it was really slow. I cant play games like I used to and for example the game rust I play it on max settings and would usually get 70-90fps now I barely get 30fps and for runescape I play that maxed at 50fps which is the limit and now its 1-6fps.. idk what the problem is... I scanned for viruses and updated everything on my computer and restarted it multiple times and cleaned the inside which barely had any dust.. if anyone can figure a solution please let me know asap, thankyou.

 

[Zackattack97]

oh and when I open up my task manager my cpu levels,memory level,etc are all at perfectly normal numbers