Sex after sexual trauma

My birth father sexually abused me from age 6-12. I eventually told and went into foster care, where I was eventually adopted. I suffer from PTSD. I have nightmares almost every night, and flashbacks about once every few months. My fiance and I are very close, and he knows about my childhood. I am afraid that when we have sex for the first time on our wedding night, it will trigger me into a flashback. I love my fiance and I want to make love with him, but at the same time, I am afraid. What should I do to overcome this fear?