It sounds to me like he's not getting enough to eat. He won't poop if he's undernourished. 3 oz. every 4 hours is only 18 oz. in 24 hours. A 6 lb. kid usually eats a lot more than that, especially now that he's almost a week old. I don't raise bottle babies, but from what I remember of the few I've had, kids that age are usually finishing a 16 oz. bottle at each meal, and I feed them 3 meals/day. Healthy growing babies drink a LOT of milk so I really think the lack of poop that started as constipation may now be due to not enough milk. Too little milk can also cause dehydration which in turn causes constipation.Over the last two days, he's extremely hungry so I've been feeding him 2.5-3oz every 4 hours, checking his tummy. Overnight, he's in a bin so I can tell where his poop goes...but it hasn't gone? I can't see any stool at all and it's been 24 hours since the last enema. He is not pacing anymore. I think I'm going to do more enemas just in case.