First off, shame on your parents for not being supportive! As a mom what I want most in life to to see my kids happy, I would hope all parents want the same, but I guess not! Sorry, but I'm angry for you! Anyway, tell them you are joining the military, maybe that will be enough to snap them out of their ********? Also, I'm assuming you are female (sorry if I'm wrong) but I know some that work as live in nannies for families and they go to school and on their time off they babysit and live in the house with the family. It provides a place to live plus a job and time to go to school. My friend has a girl living with her so she can go off to work as a midwife at any hour of the night, then the nanny's job is to get the kids off to school and then she goes off to school herself. Anyway, it's an idea. I do think the military is a GREAT option for you, I think I might have done this had I not got married and had kids at 20.
Also, if you went away to school where you lived in a dorm, using loans and paying what you can plus scholarships, would they allow you home on weekends/breaks/summers? Maybe just going away to college and living in a dorm is an option? Anyway, good luck hun, I'm sorry your parents are making your life so difficult. Though being a doctor isn't a bad option, maybe consider it?