LoL Client

For some reason my LoL Client randomly stops and closes itself out. This is super annoying cause I'll be in Champ Select then then the client would stop and when I re log in, I would have to wait out the punishment of backing out of a champ select. Also when I do manage to get into a game, the client would end immediately the moment i go into the post-game lobby. And has anybody else notice random fps drops? My game used to run on like 60-70 fps with really good graphics but now I run like 4-17 fps on potato quality. This is really pissing me off someone please help.. :'(