Baby not rolling or putting weight on legs

So my daughter is 5 1/2 months old. She was born at 36 weeks. Every check up so far she has been right on track. However, her 6 month appt is coming up and I'm planning on bringing up a few things to my pediatrician. I'm a FTM and I understand all babies develop at different rates but my daughter will not roll from tummy to back or back to tummy, seems to really struggle sitting (she can sit assisted but will topple over the second I let her go), absolutely hates tummy time and will not push up on her hands and will not bare weight on her legs for more than a few seconds. I get emails every month from the hospital I deleivered at telling me what milestones are important for them to reach at a certain age and she seems to not be meeting them anymore. Am I overthinking? Has anyone else been though this and everything turned out fine?