Why does my outer wrist joint hurt?

I am a 15 year old female and i just starting playing tennis for my high school team. Its the third and last month of my season and my wrist joint started to hurt. When ever i return the ball with my racket the recoil makes my wrist hurt. So i wrap it every time the team has a match. but i was just wondering, does it hurt because I'm hitting the ball wrong or because i just started playing three months ago?