Okay so I'm 13, and Im so confused with myself.?

Okay so I'm 13, and Im so confused with myself. I happy one second and sad the next I'm never just content? I handle my problems by bottling them up, I wouldn't kill or cut myself. But by keeping them to myself gives my more problems. I try to talk about it but I feel that I can't explain myself all the way? I feel so happy being imperfect and then I just feel like I'm lying to myself I'm so sad that I'm not? I never can make up my mind. I don't like making scenes so I wrote everything down and keep to myself. I'm good at hiding my feelings to so if you saw me at school you'd probably just see me as lucky with lots of friends, good grades, very athletic. But I'm not satisfied with myself at all. Again, I handle my problems better than most I wouldn't drink or do drug dont plan on it either. I keep my grades up all a's yet Im unhappy or really happy, never somewhere in between. What's wrong with me?