My baby is 14 wks today and still not using her arms at all to prop herself up when we do tummy time. I position her arms for her to help her along and have tried using a support pillow, but she doesn't even try using her arms, which means she hasn't rolled over yet either. She isn't able to get her head up very high either (not sure if that's because she has a giant head? 99th percentile!). She has been great at getting her legs underneath her since she was only a couple weeks old, so it seems maybe she is developing "backwards"? I hate to say this because I know all babies do things on their own time, but there are general milestone timelines in place for a reason, so I'm a little worried my baby is getting a little behind on where she should be?