yep... i totally and wholeheartedly agree with kristinc as well. (dh is a chiro, but, alas, a sports physician)
my daughter had problems when nursing on my left side, but she was adjusted at 3 weeks old and was great after that. we also made a special trip at 6 months. she also was very "poppy" and it was very reassuring to find out that she was ok. her back would crackle and pop quite dramatically when she was picked up. turns out we were inadvertantly "adjusting" her by our hand positions when picking her up.
we have to bring reece in to dh's ped chiro friend. hopefully it will help with his carseat issues...