My son will be 9 months old soon. He does everything he should except for sit up on his own. He crawls, he pulls himself up on things, he will sit up on his knees with his feet under his rear – but he will not sit up on his own on his rear with his feet in front of him. My girls were sitting up on their rear before they even started crawling. I am really starting to get concerned. I have made an appointment with his pediatrician but it is not for another month and I would like to have an idea of what is going on with him before then.
It is unusual for a baby to be already crawling and pulling to stand, which is doing on time developmentally, but not sitting independently. Your son may have weak trunk/core (belly muscles) and need some strengthening to help him achieve independent sitting. I am glad to hear that you have an appointment with your pediatrician. I would also suggest calling your local early intervention provider and requesting a physical therapy evaluation. A PT would be able to give you some specific ideas for trunk strengthening exercises to help your son achieve independent sitting. I could not find specific early intervention information for your city, but this link has a list of contacts for outreach for early intervention in Louisiana and hopefully one of these folks is in your area and you can call them to make a referral for your son or to get more information.