Trying so hard but his behaviour scares me

My boyfriend n i have been together for 2 yrs but have known each other for close to 20. He has GAS n lately he's been flying into full blown rates. I try to reason with him but it angers him more. Things are getting broken n the apt gets trashed. Hi behaviours n fits are starting to scare me. I've been in several emotionally, mentally n physically abused, one of my abusers was friends with him. I left a narcissist before we got together. His behaviour is triggering past memories and situations n is really starting to scare me. I also had 3 grand mal seizures not long ago. I know he would never ever hurt me but this is exacerbating my alters cycle n I'm almost at my wits end. Please help