I wish I could help, but I'm kinda in the same position. Nothing I do is ever good enough for my mom. She very strict and barely lets me do anything. I live in the shadows of my older siblings.. But this is my last year of school. The year I've been waiting for. I'll finally be able to leave and be independent.
Hmm... you are mature in how you handle your life I suppose at your age. Perhaps your mom has forgotten what kids are like and is seeing it thru an adults/parents eyes. Parents often are blinded with their own children for better or worse. But if you at least have an open channel of communication with them, you should discuss your issues.
I was pretty much in the same position last year, it's not so bad this year as I'm seeing a psychiatrist. But anyway, I know what you mean.