My first son didn't crawl at all, ever. At around 7 months he began to ROLL across the floor. He'd get halfway to what he wanted on the other side of the room, look up, realign himself so he was aiming the right way, and continue rolling, it was kinda funny! "Educators" have said that crawling is necessary to train your brain to work and be a good reader, strange as this sounds. You use opposing hands and knees to crawl, and doing this action trains your brain for the "way" it works to read. Some adults who never crawled who cannot read are even taught to get down and crawl in an effort to help them to read! Bizarre as that sounds (I have a few teachers in my family, I, as you can tell, am not one of them! LOL) anyway, in the end, my son who never crawled is an avid reader, go figure! So there are always exceptions. Don't worry though, I now have 5 kids... and they all crawled at their own pace, eventually (except Tony, the roller). All at different times. Gina, my 2 year old, didn't crawl until she was around 8 months. Crissy was earlier, she was around 6 months. I think the more you make them have tummy time, crying or not, the more they'll develop the strength in their neck, arms, upper body, and the faster they'll crawl!