Why am I cutting myself?

I don’t have depression. Yes I get sad but I never cry, and I never talk to anyone about it. I have anxiety but it’s been mostly manageable. So what has been happening recently has surprised me. Lately everything has just been to much. The stress of school, sports, clubs, friends, my ex boyfriend, etc has really just gotten to me. All of a sudden I just feel frozen in place. I can’t get myself to get up or be productive. I’ve also been feeling this strong hatred towards myself. I feel fat and ugly and useless. I hate how socially awkward I am and the stupid stuff I say. In the past when my anxiety got bad I would dig my nails into my thumb until it would bleed. Then a year later I started using a pocket knife to cut lines in my thumb and my hand. Now I’ve been cutting lines both there and on my wrist. I don’t know why im doing this. Am I actually cutting myself? Why am I doing it? I need help. I have a really good life. I don’t have a tragic past or shitty parents. So why do I feel this way?