boyfriend scared me last night

Note: he has a very dark, troubled past and can be extremely violent if he wants/needs to but hes never hit a woman nor does he want to

so I've been with my boyfriend for 18 months now and I love him, I also love when he chokes me....when we're both concious.....

so last night we were sleeping and he turned over and put his arm around me and put his hand on my boob like he usually does throughout the night. it woke me up because I'm a pretty light sleeper

when all the sudden his arm started twitching almost. so I thought "oh he's having a bad dream" so I went to wake him up by turning onto my back when next thing I knew in a swift motion his hand went to my throat and he started choking me to the point where I actually started gasping for air, it all happened soql quickly. that I yelled his name and he stopped choking me and woke up and in a sleepy voice was like "what?"

I didn't recognize the man who was next to me and I ran into the bathroom, and sure enough I had red marks all over my throat and down my sternum, and I find myself shaking from all of this

while I was in the bathroom trying to process it all he came in and was like "Hun what's wrong?" in his usual sweet voice I just stood there frozen looking in the mirror so he turned too, when he saw my neck and chest and was like "what the fuck? what happened?" so I'm like "you choked me..." the look on his face could've broken my heart. he just went into the bedroom. when I came back in the light was on and he was laying there blanket completely covering his face. I was scared to lay next to him so I sat at the foot of the bed, he felt this and stood up and was like "are you ok Hun?" I didn't want to look at him so I responded with "I'm scared of you right now..."

I felt him come across the bed to where I was and he started kissing the back of my shoulder he said "you know that was nothing against you right...? I would never physically harm you unless you wanted me to (sex) I'm so sorrry"

I turned to face him, smiling now, I knew he was speaking the truth and so I kissed his cheek and asked why it happened in the first place, he confirmed it was a bad dream, so he thought he was choking the guy only in his dream, so I told him its alarming in his sleep he was able to find my throat and actually start choking me, he asked if I wanted him to sleep on the couch for tonight, and as much as that made sense because of how much he scared me last night the thought of him sleeping anywhere then right next to me scared me even more.

we've decided to talk more about it when he wakes up and see what to do about it if it ever happens again.

in the 18 months I've been with him he's never done anything like this before so I'm starting to believe it was truly an accident persay

UPDATE:: We talked it out, he apologized over and over again and he's open to looking into getting some help or exploring options. in the meantime we're just really glad that I'm a light sleeper and that it's never happened before

I love him too much to be afraid of him or distance myself