Advice...about past abuse

I was abused by my ex for 8 years I am now with my fiancé, father of my son, I’ve always had night mares but never where I wake up screaming till two months ago I kick and scream and try to get out of bed and my fiancé tries to calm me down but I can’t, (there was one time I got drunk and thought my fiancé was my ex and went basically crazy)...I’ve been with my fiancé 3 years now and I feel like I need to leave the relation ship...because this is not what he signed up for idk what to do...