If you click on your picture and look at the list of questions you've asked, there are a number of them about eating and pains in your tummy. My GUESS is you're stressed over something but that's just a guess. Nobody can diagnose medical problems via the Internet. Talk to your parents and ask them if you can see a doctor about it.
If the doctor is unable to find anything wrong, accept that and try to figure out what's bothering you. At your age you should be playing, having fun and doing your schoolwork, not worrying about your health. There is a reason for every way you feel. Try to understand the reasons and deal with them.
