Literally, of crap! I can't seem to find a diaper that can contain this boy's bowel movements! If I put the diaper on nice and snug, he craps up the back. If I put them on looser, it comes out the legs. He is 17 lbs and in size 3s. They are definitely not too big, but he is still 5 lbs away from 4s so they can't be too small yet. I've tried pampers cruisers and baby dry, luvs and huggies pure, and little movers. Is it possible that I need to move up already? Is anyone else in 4s? Or any other ideas?