MMR Bug

My mmr drops literally over night. I play get it up, then it drops when i wake up. Why does this happen? I win 18 points a game and lose 13 at night then i wake up, play ranked and it dropped back to where i lose more points then I win. It literally makes it impossible to play ranked or league in general. I doubt im the only one with this problem so please fix it. It is depressing and drives me away from league and probably others too!