I'm a ftm with an 11 month old lb. I'm getting worried about his development because the best he can do movement wise is roll around. He cannot get himself into a seated position from a lying down position. He cannot crawl. He cannot pull himself up (and shows no interest in doing this). If I put him in a seated position he'll happily play with toys around him. However he cannot work out how to go from his seated position to lying down and sometimes just falls backwards or goes head first into the floor to get there. I give him plenty of floor time but he shows no interest in learning how to do anything. Also when I stand him up he locks his knees and cannot stand on his own but leans on me while standing. Any ideas what I can do to develop his gross motor skills?