Game runs terribly now for no apparent reason.

Played this game a few days ago, worked just fine. Play it now, I get constant microstutter. It makes the game unplayable since I'll say to do something, it will stutter, and my input is completely dropped. My mouse will also freeze in place even when I'm moving it. Strangely enough, it's a lot more manageable playing jungle than bottom lane, but it's still horrible to try and play with. It isn't ping spikes, my ping is constantly in the 60s. It isn't tanking frames, my frames remain well over 120.