Why does he excessively bring up his girlfriend all of a sudden?

My guy friend just recently got into a relationship with a teacher at my school that is twice his age. I barely talk to him but whenever I do he excessively brings her up through text to the point where it's just annoying. Idk what to do because its clear I definitely don't like him in that way since I've told him I'm with someone else and these two have been dating for not even a month now. I'm just confused. guys help me out