I'm sorry you had to hear that from him in his sleep. That would upset me for sure. But then again, it is only a dream. If my husband talked about his ex-wife in his sleep, I would probably laugh.

My sister, who is married, had a family friend. This friend of her husband, too, would enter her dreams and she would wonder why, then just brush it off. At parties, she drank and became a little flirtatious with him, but she assured me she never had feelings for this man. She wondered why she kept having dreams of him that were kind of like they were involved.
Well, fast forward to now, her husband is living somewhere else, and she is dating this man.
Maybe dreams do tell us something? I don't know. Just wanted to share that one instance with you.
Dreams are messed up, though. So, maybe you are just fearing marriage?
Or you could be desiring your best friend. Which is quite possible.
12 years is a long time to be with somebody and that's around the time some people seem to "wander". That's just my thought.
Hope all works out for you.