Xander is almost 4 months old. He hasn't had a wet diaper since 4:30 (it's 9:30 now). He seems to be acting normal. I nursed him at 6:00 and he seemed to be eating normal. He usually pees shortly after eating, but hasn't yet. He went to bed at 7:15 and I woke him to nurse. Still no wet diaper. He's nursing now like normal, but should I be concerned with the lack of peeing that's happening?