Wow, I cant relate you your struggle so much.
This the same thing I went through with my husband. Before we got married we were together for 3 1/2 years. Every time I brought up marriage he said he wasn't ready, but he would not sit down and really tell me why. He did say that he needed to figure stuff out with himself. But not details. I had known about his CSA our whole relationship but it was something I knew to not talk about. I eventually got fed up and moved out. It had seemed like the more I pushed the meaner he got. I told him that I was leaving him because I wanted to be married and have a family. If he didn't want to marry me I would find someone who did. I told him I loved him so much and hoped that he could figure his stuff out because I felt that all the anger he was projecting on to me was because he is really mad at himself.
3 months later he came and begged me back. He got me a ring, at first everything was great. He was so excited, and helped plan everything. However in the days right before the wedding he started getting really distant again.
We have been married for year now and let me tell you that the shit really hit the fan. Because of his CSA he feels like I don't really love him, and he isn't good enough. We are trying to get some help for him. A good therapist. But I will warn you that this is Hell. Sometimes I wonder if I should have told him to go to counseling before we got married, however part of me thinks that the reason things got so bad he is finally dealing with them, is because we are married and he feels more secure. I don't know, my husband is 26 and I'm 27 he is a great provider but emotionally I'm on my own. It's hard, painful and exhausting. Be careful what you wish for, because if you guys get married before he has healed you could find yourself in a hard situation.
Keep calm and carry on!