please help me

Am I anorexic? I don't think I'm fat and I don't starve myself to lose weight, but I starve myself  sometimes since I feel like it's reasonable punishment. I made my boyfriend mad once and skipped lunch and dinner, I failed a test and skipped all my meals the next day, and today I was ashamed of myself and disappointed since I was too scared to try out for a sports team so I skipped lunch and soon dinner... I do it in other ways too, like sometimes I will hold on my urine for a long time if I feel like I've done something wrong, but until it gets too extreme then I will use the bathroom.
This has been happening ever since I was in elementary school, but I've never told anyone about it since I'm ashamed of myself for doing it. As you can see though, over the years I've just been doing it more and more. I don't know why I do this to myself, I don't know what's wrong with me, but if you do please tell me why I'm like this and how can I stop. I'm 16 now