I am genuinely afraid, that my boyfriend might be having some... condition or dark side he is trying to suppress. What could he be battling inside?

Alright, my boyfriend, who i got back together with. I always knew he is somewhat... psychotic. Different. Primal. Dangerous. Polarizing. Because damn, he may act completely different from himself, the other day. I always knew and felt of this dark side of him. He can be sadistic. And i like that, because i can be masochist.

But sometimes, his behavior switches, he gets drunk on squeezing me. He might even slap me somewhere... sensitive and will keep his hand there, to... feed on my pain... with this... cruel look on his face.

But damn, less that two days ago, in the middle of the night:
We sleep together, in the same bed and it seems he had a bad dream or something? Something about women, because I woke up hearing - "fucking women". Still don't know if it was like - sex-ing women or damning women.
And he was holding one side/half of his face with a hand and was struggling so hard! It seemed like he was in pain, as if he had a serious headache. I asked him what's wrong and gently put my hands on him.

It was a mistake...

Like in a horror movie, he looked at me, with that only eye, which was not covered and it... just.. wasn't him. I did not recognize the guy i love in there. Instead... it was dread... I felt dread. A pure terror. As if something capable of and wanting to hurt/kill me, was looking at me. Then he blinked few times and as if he snapped out of it. He said we should get back to sleep. And he lied on the bed and i kid you not, he just fell asleep, like that!

Yeah, i didn't sleep the rest of the night.

Yesterday we worked out, we ran, then we went shopping. I saw him on two more occasions grabbing one side of his head and struggling... then just tells me he is fine.
Honestly, i am not sure how safe i feel with him, anymore. If at all. I mean, he told me he would kill for me, and i could tell he wasn't joking. We sometimes go out, with him wearing a pocket knife or even his gun, loaded. I mean, i feel safe from other people with him. But not from him..
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Addition:

Yah, we talked about it and he said he will consider visiting one of his two psychotherapists. But yeah, he definitely needs to visit, not just consider! Makes me feel so... unsure...
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Update: he has an appointment in approx. 36 hours. He is a man of his word, after all.
I am genuinely afraid, that my boyfriend might be having some... condition or dark side he is trying to suppress. What could he be battling inside?
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