My 7 month old is very cheerful and has started to babble after a quiet period, but he HATES being on his tummy, and can't lift his head up from the ground for long. He's had a gut problem for a while, and i don't know if its affected his development. He sits up well, and wriggles on his back, he can roll from front to back, but not vice versa. Is this in the normal range? I really don't think he will ever crawl at this rate..