The more time goes on, the least responsive alt+tab becomes.

I'm having immotivated lag these days. So I continuously have to alt-tab to dc/rc to see if it might fix it. And with every patch, it works less and less. I'm forced to ctrl+alt+del, then start Task Manager, then it sends me back to LoL, then I can alt+tab. And today, these shenanigans fucked my PC up completely, and I went down to 3 fps for the rest of the game. HELP