my son is 4.5 month old still he is not even trying to roll over. I m really worried. his head is strong. he s watching all sides when I move here to there. he is looking even slim only his birth weight is 2.670 and his yesterday s weight is 6.3. if my baby is lying if I just give my both hands to his hands he wanted to getting up interested to sit. even if I full his stomach with my feeding after I put him to lying to bed he is crying after 10 min if I take him he s silent and watching all sides. if he didn't lying down how can he roll over. pls explain me doctors