How do I deal with Guilt?

I was 12 when it started. My older sister made “passes” at me and I really didn’t think much of it. She then started touching me, my privates, tickling me. Still I was so blind to it. Then she progressed to oral then full sex. I am 14 now and this has stopped. I said no once to her and it ended. I am feeling so guilty though because I have on a few occasions welcomed it. What can I do to alleviate this guilt and also to try and restore some semblance to our relationship as brother and sister?