whats he doin?

Me and my boyfriend have been happily together for half a year. BUUUTTT theres one thing that bothers me so damn much.

Nearly every other night he wakes up and says he had a dream of me cheating or breaking up with him or something along those lines.

He hasnt once actually convicted me of cheating, but always has these dreams.

Also, he talks about my exes a lot. Not all the time but enough to where ive had to ask him to stop it.

What could this mean? Because he knows damn well i havent cheated nor i ever will.