like a regular roommate with whom I argue every other day and never have sex...

conflict can damage attraction so those regular arguments likely aren't doing your sex life much good.

she likes to tease me a LOT - for example when she's changing clothes and turns her butt towards me, but whenever I go to her and try to initiate something, she stops me. It's really frustrating.

I don't think she's teasing you, she's turning her back on you to change her clothes, which would make her really bad at teasing you if that's her intent.

I also have a hard time communicating this sort of thing, because I don't have confrontations which I know will lead to long and heated arguments.

not communicating is really damaging to a relationship. communicating properly doesn't involve arguing.

It sounds like there's a whole lot of arguing and conflict in this relationshipn, as well as very little communicatio, that maybe you two just aren't that compatible both in and out of the bedroom?

DB aside, why could you want to marry someone you argue with so often and you can't discuss things properly with, without it being a long and heated argument?