He just turned 7 MO he doesn’t sit on his own yet. Idk why but I’m getting a little worried. I always have him on his walker he loves that thing he walks runs on it can get out between our small hallways he manages to get his way back/out when he gets stuck. He loves it. But whenever his not on it I do try to sit him on the floor or my bed and he hates it he will go to the side

I feel maybe his not ready? Even when I sit him on my lap he goes backwards or will move down as if he wants to get off. He hates sitting down he will rather have me stand him up. I feel like maybe his going to crawl late too since he doesn’t last on his belly should I talk to his pediatrician?