Black screen than crash bug

today and yesterday ive had a bug where in game my screen would go black my monitor would disconnect and my league client would crash bringing me to bug splat. ive looked around to see if anything even remotely close to this and havent found anything. the screen would go black the monitor would disconnect for a few seconds and either go back to game or crash, if it came back to the game it would only be literally a minute before it would happen again. if anyone has had this happen before could use the help