What can I do about this situation?

Well I am 17 and I have been living with my mom all my life until summer of 2008 when I decided to try living with my dad. Things were ok at first but after about Christmas things were starting to get bad. Things were better at my Mom's so I wanted to move back with her. I only told a few people about my decision but someone who knew my sister told her and then my sister told my step mom. I just found that out last weekend and I am scared to death about what they meaning my dad and stepmom are going to say to me. I am not sure if my dad knows yet but it won't be too long now. I didn't want to tell him before I was done with school for the summer because I know that once I do it will be VERY stressful and I didn't want to have to deal with that and school. I really could use some advice on how to handle it. I love my dad very much but I am happier living with my mom.