Parenting: Friends Talking Community

My ex-husband and I seperated over two years ago when my daughter was 2. Since then we have shared custody 50/50. We don't have the greatest relationship communication wise but we have remained civil throughout. I don't say bad things about her Dad to her and I'm fairly confident he doesn't say negative things about me (his family members may be a different story). My daughter seemed to deal with our seperation pretty easily since she was so little and I think we did a good job of sharing equal time, kept her with the same daycare provider, kept her on the same schedule, etc. Now that she's older she's asking some questions that are making me think I need to maybe try and explain some things as simply as I can to her. Like sometimes she tells me she wants me to come spend the night with her at her Dad's and I have to tell her that I cannot. Or she will say "You and Daddy aren't together anymore" but she doesn't ask any questions about that. When she asks about me spending the night at her Dad's house I usually just respond by telling her that I cannot stay at her Dad's house because we don't live together. I have my house and Daddy has his. And I tell her that I love her very much and so does her Dad and that when she's with her Daddy that's her special time with him. I'm really feeling guilty about the whole thing and I am seeking some advice for how I can explain all of this to her.