My DD is 6 and a half months old. She can fully sit up by herself without being propped up and is gaining leg strength with her jumperoo. I feel like she's a little slow with rolling and trying to crawl though. She's always absolutely hated tummy time, seconds after being put on her tummy she cries so we've just not done it much. I think because of this she can't roll over and I don't see how she's going to learn to crawl either. Any advice?