I have a 10 week old and she absolutely HATES tummy time. My doctor says that some babies are just like that, and there's not much to be done about it. However, I read that tummy time is necessary for arm, back, shoulder and neck muscle development. So if my baby doesn't get her tummy time, does it mean developmental delays? Will she not be able to hold her head up on her own very well, or will it take her longer to be able to do it?