Most Helpful Girl
I can say that the most guys react the same way based on my personal experience and also friends experience.
The difference between a guy and a girl when in a relationship is that when a guy feels some kind of comfort they stop feeling the need to keep talking to you, because they already know you're his, you love him, you will be there and u can wait for him because there are feelings involved. Which I think is really selfish and makes them into kind of assholes.
But girls on the other hand get used to the attention and they expect the saaame treatment all the time. Which guys can't get into their heads for some reason.
I don't know if even discussion will help honestly but you can try. And I would get upset in your place and it's happened before, I agree it's terrible and you have all right to be upset.
Most Helpful Guy
The chase is the start of the fun contact shouldn't die down due to you being official. Sounds to me he can't be bothered with the effort. You need to remind him once you have a girl you still need to keep up the effort to keep her or someone else will