My son will be 4 months tomorrow and I must admit I didn't do tummy time nearly as much as I should have bc he absolutely hated it and would scream forever or go straight to sleep no in between. He holds his head up okay he has lazy moments but he can does it. But I saw some pictures of some of your babies looking like they are sitting up by there self. Should I be worried should he be doing that? I have a play saucer we are slowly introducing to him that requires him to sit up but it's a slow process we can only do about 10-15 mins at a time without getting cross. What physical milestone should a 4 month old have down?