I felt the same way when I was in high school, more or less, although I never got any grade lower than a B because my school was highly competitive and there was peer pressure to do well academically. Thinking about college used to make me really upset because I felt like it was this thing I was being forced into and it was stressful, but now that I'm actually in college, I have to say, in various ways it's better than high school. If you do enjoy learning, there are a lot more classes you can take, and it's less restrictive overall.
High school is a lot of stress, I'm not surprised you want to just give up and walk away. :/ If you can, you might try taking classes at a local community college while you're in high school, though. It could make you feel differently about things.
I'm sorry your family isn't more understanding. I don't really know what to say about that... Do they just get mad you can't do everything on your own or do they offer to help at all?