It happened to me once something similar.
I fixed it by disabling steam ingame, I don't know why it happened and why it worked, but it did.
Also, if you want to play competitively but don't want to lose the good graphics, disable AA, ambient occlusion and post-processing, your game will still look good and you get much more FPS
TBH, I don't care about comp. I'm trash. I'm ranked Silver I.