Why am I gaining weight?

I am 14, I am 5 foot 3, and I weigh 116 lbs. A few months ago, I weighed 112. At first I was gaining weight I think because I was eating a lot and not exercising. So I stopped eating so much, joined a kickboxing cl, and I go twice a week, and since I started doing that, I gained two more pounds! I feel a little bit thinner, so I decided to weigh myself and I was shocked, what is going on?