It can be a very scary feeling. For me if I try and control the fantasys or push them aside they get worse, dreaming is really bad because it's so Vivid and I really can't escape it.
I feel deranged and disgusting at times.
I've had trauma when I was little somethings I can remember somethings I can't, and only recently spoke to an emotional healer about one of the main issues, she explained to me that the situation wasn't me, and didn't judge me, it made me feel a little bit more comfortable with living with these fantasies and memories.
I'm still yet to talk to my psychologist about it, I'm 24 and even though I'm aware and I can live with these issues, I still feel I need a lot of work done to really let go.
I don't know if the fantasies will ever stop, but I try not to bring myself down too much when they occur.