It is my speculation that the nightmares are your mind's way of getting over the pain of the past. It's a long battle but it can be comforting knowing that each nightmare (as terrifying and horrific as they may seem) mark another step to getting over your CSA and moving closer to freedom. You're moving towards that finish line. I'm sure you've heard the old fable of the turtoise and the hare. (forgive me if my spelling is off). The hare raced to the finish line but got overconfident and tired. The turtoise took his time and won the race. The turtoise had that one in the bag. One thing at a time my friend.
This one may be scary but this might help you. A little trick I learned, was to write down everything I could recall about a memory, or in your case, a nightmare. It's important to make sure you have someone to talk to in case things get too hectic. A therapist perhaps. It's important to ask yourself "am I ready for this now". Perhaps, wait until you feel at your best and you have plenty of time to relax during and after. Anyway, you can set an alarm fo 20 minutes before you start writing and freewrite about the dream. It will reveal many things about your experience and help you to identify it, deal with it, and eventually conquer it. The 20 minute time period makes sure you don't over do it. Spending too much time on a situation like that can be very taxing. Dealing with harsh memories and nightmares can take a lot out of you and it's important to take care of yourself so that you have the endurance and strength to deal with everyday life situations outside of CSA.
Just some food for thought,
Truth is the very reason we strive to live. It surrounds and resides within us. Accepting the truths we already know and seeking out those we do not is a direct path to inner balance and joy. For life is not a means to an end, but a journey. Life comes and goes but the truth will always live on.