Ds2 is nearly 9 months old. He's nowhere near crawling yet & gets angry & upset on his tummy. He's quite happy to sit for ages playing with his toys,reaching, stretching & grabbing (sometimes to the point he topples forwards!). Put him on his tummy & within a few minutes he's crying to be picked up. We've put toys nearby, within in reach etc.
Although I'm not worried too much about him not crawling the tummy thing does concern me - if he hates being on his tummy how will he ever learn to crawl?