hi my son turned 5 months old last Sunday. He hasn't rolled over and he doesn't kick his legs much. if we place him on the mat he will be almost in the same position. he will bring both hands to mouth and will grab objects in his mat. But he will not kick his legs much.He is bearing weight on his legs and trying to lift his head and chest when he is lying on our lap. I'm very worried that something is wrong with him. most of the babies would have rolled over by this age and will kick their legs a lot. Please advise