Anyone else's 9 month old still

Janice

not crawling? He rolls over from his belly to his back and from his back to his belly. He sits up unsupported. He only falls over if he is reaching for a toy or gets overly excited. He still isn't crawling though. He won't even try. How can I get him on his hands and knees? I try and he pushes his legs back and gets on his belly again. He stands with support for a couple of seconds at a time which is a very recent development.