Permanent FPS drop of 50%

I play the game on my laptop with graphic settings on the lowest, and mostly achieve a stable FPS of 80+ . Earlier this week I was playing, the round ended and when the next one started, my FPS had dropped to 40-45 where it stays permanently.

What is weird that it just happened during one game session, and not after a game update or GPU driver update. The FPS is still around 45 when I play and I have not found a fix for it. Is anyone else experiencing this issue?

Windows 10 64bit
Intel i5 7300HQ
Nvidia GTX 1050 2GB (driver version 436.30)

Same getting unstable fps and some stuttering at the sentence area all map when too much chaos, I using Amd Ryzen 5 1600 6 core, Nvidia Gtx 970 vram 4GB , ram 12 GB

I updated my drivers (Nvidia 440.97) and the problem still persists. My FPS was higher when the game released than it is now. Even though I just dropped my FOV from 90 to 85 and resolution scale from 100 to 80 but it still didn't get my FPS to what it was earlier, only to about ~50. The problem is with every map, in custom servers and normal matchmaking.