Well, the promise ring.. doesn't that represent a promise for an engagement or am I wrong? At the same time, since he says it's too soon for him to know, I wouldn't push it.

If you don't feel comfortable moving in together before knowing that you're "the one", then don't do it yet. You can say you're not ready for that.

It is only five months into the relationship. Relax, sit back and enjoy for now. I wouldn't worry so much about a marriage with this person yet. It is far too soon to really know or to be talking about it. He is being smart and is taking his time. Nothing wrong with that. It takes a long time to really get to know a person fully, inside and out.