My husband decided to 'grow up' a lot after we got married as well, taking work more seriously, etc. Could be your hubby also now recognizes that he has responsibilities to uphold and a future to secure (with/for you) now that you are married.
It has resulted in my husband being more distant from me sometimes as well but we women need to remember that men have the kind of focused awareness that tends to block out everything else (bless them

). it's hard not to take personally sometimes (particularly when you are used to getting more from him) but it seems to me that he is doing it with the best intentions.
If you say that nothing else has changed, then I wouldn'y worry about it too much. This is what grown, responsible men tend to do.