DS is 7 months old. He's been crawling since he was 5 months old, and rolling both ways since he was 4 months. He's trying to pull himself up on things and can stand by himself, holding on, and when he's crawling he often gets right up on his feet (head down, bum up, leaning on his hands) like a yoga position.
He will not, however, sit on his bum!
Every time we try to sit him up, he arches his back so that he's laying down again and rolls over onto his belly. Or he just falls over to one side or flops onto his back (and hits his head, and cries ). He won't even sit leaning forward on his hands if we prop him that way, he just keels over.
He's extremely strong so we know that he could do it if he wanted to. He just won't. The only time he 'sits' is on our knee, and he's done that since he was about 4 weeks old. Even in his highchair and stroller he slumps, and won't sit up.
The closest he gets to sitting is kind of laying on one hip, propped up on one arm (his favourite playing position).
Is this normal? When will he just sit up by himself? I'm starting to think he'll be walking before he can sit