Thanks for all of your replies! I don't know how to bring this up. I'm sure I should, but I will sound jealous and I'm not sure what I'd expect him to say.
Obviously he has a life and can date whomever he chooses. Obviously it's healthy for him to date vs the alternative id prefer where he sits at home alone jerking off to fantasies of me and only me.
If say she was much younger, at least 15 years younger...