As advised, therapy will work if he wants it to work.
It's a long way from a cosy chat about flirting. A professional therapist will fillet his subconcious like a fishmonger fillets a plaice. They will back him into emotional corners, and make him face his behaviour. it is not pleasant, and to go through it, he eeds to be really sure he has a problem, and he wants to stop.
I think your partner is taking you for granted. His behaviour is juvenile and disrespectful - even more so because you have pointed out that you are hurt by it, and he continues.
You need to have a serious talk about your future together, including the fact that if his infantile selfishness continues, there won't be a future for you as a couple.