I Got Hacked

So I woke up today, got on league, and checked my match history. There are two games of Ezreal in AI and a Yasuo game that I've never played. I went in a game later on and my whole settings was messed up (key binding, etc.) This happened yesterday too. The person played Braum and Wukong yesterday and had my settings changed. I don't know how my account got hacked twice...I'm worried that the person will start to mess up my rank and spend my rp/ip on things. I just changed my password just so the person won't hack my account again...Also, I checked my match history and the hacker bought Yasuo on my account when I don't even play yasuo...