Should I be worried that my 9 month old won't kneel...in fact she screams if I try to put her in that position. She isn't crawling or standing, she sits up well and pushes up on her arms well during tummy time. She has only rolled over twice (same direction both times) but I figure she can do it she just chooses not to. I just worry about the kneeling thing because that will help her crawl or learn to stand herself right? Thanks