Is my boyfriend's behavior abusive?

[starlitsara.livejournal.com]

Potential triggers. My boyfriend is normally a sweet and loving guy, but when we are intimate it's like he becomes a different person.

He makes disgusting comments about my private parts, saying they smell rotten, and talks about me being all stretched out from the other guys who have been down there. But I was a virgin before him. He constantly accuses me of cheating, but then talks about how hot it would be to see another man taking me against my will. He calls me degrading names and tries to get me to call myself those names too. He does other weird stuff like punching himself in the head when I'm going down on him. Once he even spit in my hair and I started crying. That was only once, though, and he apologized but he admitted it got him excited to see me cry.

When we're not being intimate, he is completely normal, but this stuff scares me sometimes. Is it abusive or just strange and what should I do?