HI,
I would agree with the other two physios who posted excellent answers above.
My thoughts when thinking about the problem as i was reading was that you have a combination of overactivity and underactivity with postural changes leading to lots of compression on your hips.
Janda was mentioned above. Shirley Sarhmann would be another. Peter O'Sullivan would be yet another physio who have clinical models that deal with these issues.
If it is any help for you, i see lots of these types of "growing pains" in my clinic...exercises and stretches are definitely the way forwards.
Good luck