Did I turn bad at the game?

Bad streaks happen to literally everyone from time to time. I once went 11 straight days playing at least 3 games/day and losing ALL OF THEM. Regression is most definitely a thing in a game like League of Legends.

My advice: Take a hiatus. Take the game off your desktop, and focus on something less intensive like Skyrim for a week or so. Then come back later and get back into it. It works wonders, I promise. :)