Sudden fps drop

So, I've had this problem for quite a few days now, I basically go in battle, 60 fps even with some graphics on, all normal, but after a while fps suddenly drops incredibly much, from 60 to 10 or 5, affecting audio too, causing me to hear "disturbances", or something.

This never happened before, it happened sometimes when fps dropped from 60 to 40 because of some graphics after a while but never like this... Sometimes neither controls to turn my turret or shoot work when i press them! I did all cleanups possible, help???