Fps issues

I'm having issues with my fps. I go from 144- 90- 45- 0- and then back to 90 and go between 40 and 90 where I usually have a constant 144 fps all game. I tried restarting my computer, updating my drivers, closing everything, changed settings, even downloaded a fps booster and nothing is helping.

Is it the patch? Is anyone else experiencing this? My pc isn't that old so I'm not sure what's going on...