I love my boyfriend, but I hate him sexually. Help?!?

I've been dating my boyfriend for about 5 months now, and things are fantastic… when we're not in the bedroom. On a regular basis, around families, in public etc. he is one person and I love being around him. He's kind and affectionate, but when we are doing anything sexual I seriously think he turns into a completely different person. He tells me he wants to choke me; he leaves skin-breaking scratches; he does things that hurt and when I tell them they hurt he says, "I like when I hurt you;" and everything we do in bed revolves around his wants or needs. He doesn't go down on me, and he prefers anything else over vaginal sex (I'm clean shaven, well kept, and work out regularly… nothing nasty down there… I take extremely good care of my feminine area). He watches extreme amounts of porn, and I wonder if that's where he gets the male-domination expectations from. Sometimes I think he might be gay. I really don't know what's going on, but he changes into a monster when it comes to sex. I even saw a word document on his computer that detailed how he would find a girl and make her his "sex slave" by keeping her captive in a dog kennel… the entire document scared me. I just can't figure out why he's so great but such a creep when it comes to sex. Sorry this was so long… I'm super confused and a little scared.