I hate going to my dads house.?

you need to set down and talk to your mother, and let her know how you are feeling. At 13 you have a right to let her know being at your fathers is not working out for you and how you are being treated. Somehow it would be good if you could possibly talk to your father, a way from his other family, and let him know whats going on. Hopefully your father is just unaware of how you guys are being treated.