I see peoples babies are starting to try and sit up, be in crawl position on hands and knees, etc.

My baby is still very floppy (holds her head up tell, refuses to try and sit up or support herself at all tho) . She screams when she does tummy time still, doesn't push up with her hands yet while doing tummy time, I know shes capable of rolling, but she refuses to roll. And she surely isnt close to being on her hands and knees...

Am I the only one? Should I be concerned shes falling behind?

Anything that involves a workout she screams.. shes my lazy little chunk I guess lol..