Hmm.. I don't know if you are stalling or not, but I want to say something about the living together bit. If you two are sexually active, and spend the night with each other at one another's place with any frequency, then I don't see what you expect to learn if you live together first. i mean, if you are a slob, she probably already knows it. If she takes up 3/4 of the bed, you probably know this, too. Selfishness, money issues, all of that - you should already know about these things by now. Obviously, if you are having sex, you know if this is working out or not. Minor things can be negotiated later.
And yes, an awful lot of men use living together as a way to delay getting married.
Personally though, I don't see any real reason to get married unless you are planning to start a family in the near future, but you shouldn't be wasting years of her life if you aren't thinking you will marry her in a reasonable amount of time. There is a shelf life on her ovaries, you know.
Relax... I'll need some information first. Just the basic facts - can you show me where it hurts?