Step dad doesn't want me living here?

No, Could you all sit down and talk about it? How does your mum feel? If it is just your step father with the problem then he is the one who needs to deal with it. What is he so unhappy about? The fact that his wife has a child that she is responsible for? He knew that when he married her and you are a big part of her life whether he likes it or not. Maybe he is jealous of the attention you have been getting. It sounds like you have enjoyed your time with your mum and I'm guessing that she has enjoyed having you there too. The best thing to do is be honest with them, maybe express your hurt feelings to your mum first. She may feel that she wants you there as much as him. I hope he listens to you and accommodates you and your mothers relationship as it is a far stronger bond then their marriage.