VAC Error.

Hello, when I play CS:GO competitive, I get an error saying there is something blocking VAC system or something like that and kicks me from the game and sometimes I get cooldown. I can't join a game for the next few hours. It says I can't play on secure servers, but after a few hours, I can join a game but a few rounds later, I get kicked again when my friedns checked my profile it doesn't say I am VAC banned but it kicks me from %80 of the games because of VAC. I don't cheat nor get VAC banned. I need help please, I can't play competitive right now. Any help appreciated, and I don't get perma VAC ban which means I am not hacking so please don't say "Justice" or something like that.

VAC Error.