9 month old not crawling


My son is going to be 9 months on the 1st and still isnt crawling. He's been behind on a few milestones since birth and has had to have extra checkups because of it like not rolling until about 7 months and when we tried feeling him baby food, even thin purees that were behind his age (him being 7 months and we would give him 6 month food) he would gag on it and not know how to swallow. He can get up on his knees in his playpen and kinda just thrusts himself front to back, but wont do it on the floor. And he rolls himself everywhere he wants to go, like if hes laying by the couch and wants to be over at the toy area with his older sister, he'll roll all the way over there. Hes also been standing up and holding the couch and slowly side stepping along the couch, but still no crawling. My daughter completely skipped the crawling phase but was walking along the walls and couches by 8 months and walking on her own by 11 months and her pediatrician said that's not common so I'm not sure what's normal and what's not