FPS LOCKED TO 20

Yesterday after 3-4 hours of playing I got a directx crash. I thought that I need to update my nvidia driver but after updating it, I didn't encounter any crash but sometimes my fps are randomly locked to 20, sometimes in the menu sometimes only in gameplay. What should I do because the game in unplayable in this state, because I need to restart it in order to get the normal fps [(100+) That means everytime this happens I am forced to quit the match]. I tried to switch different setting but still no luck. Any ideas?