Yes, you have a story typical of many FTMs, so you definitely could be a trans man. Listen to LordKat and see if there's someone you can talk to at school -- whether it's a counselor or a teacher you trust. You say you don't have a GSA at school, but check to see if there's some LGBT group in your nearby community. Many places have at least some kind of group, even if its small and a bit of a drive.
Absolutely don't self-harm, you're young and will have a wonderful future if you allow the opportunity to play out. It's hard to pay attention to school when there's lots of distractions and emotional stuff going on, but try to focus on schoolwork. I found doing well in school to give me a lot of hope, because i knew that if I got into college that I could leave and start my life on my own terms. There's colleges here (in the USA) that gives you health insurance that covers trans surgeries. Not having the opportunity to go away to a college away from home may be something you'd regret later on, because you don't want to be stuck at home and dependent on your parents, especially if they turn out to not be as supportive as you hoped.