I feel as though im being used by my dad for money?

ok well i lived with my mom in texas for 14 years. my parents divorced when i was 7. my dad married my stepmom and moved to minnesota in 05. my dad and stepmom basically put on a show for me saying how much they loved me and would love for me to live with them. i thought it would be great to live with them. well i made a stupid and rash decision and moved with them. well its been a living hell ever since. they are totaly different people than they once were. they yell at me for everything. they make me do everything for them. they also make me cancel plans to help them. anyways, my mom pays $500 in child support a month and i feel as if my dad and stepmom are milking me for money. child support is supposed to cover my portion of the bills, food, clthing, and other necessities (soap, shampoo, razors, etc). well they make me buy my clothes, soap, shampoo, and all that good stuff. i went to walmart with my dad today because i needed some soap, shampoo, and a new razor. we get to the