My little wolfcub does this. When he was around 4 weeks old he hadn't been:
Day 3 or 4
Regular appointment with HV. Mentioned that he hadn't been, she said not to worry breastfed babies could go for about a week or so.
Day 10
He hadn't been over the weekend so I called HV to ask at what point we should be worried. He was feeding fine, having plenty of wet nappies, passing wind normally and seemed well in himself. She said he was probably fine, but if he hadn't been by the following day then we should see GP just to have him checked out. Suggested cooled boiled water. I decided not to give him this because he wasn't dehyrated.
Day 11
Got same day appointment. Doctor felt and listened to his tummy. Said his tummy was working fine but we could try giving him cooled boiled water or apple or orange juice to get things moving. DH and I decided not to do this, he was well, I didn't want to give him something just to make us feel like we were doing something, so we stopped worrying (mostly) because what we were concerned about was whether his tummy was working. Doctor said we should bring him in if he started vomiting or showed signs of distress.
Day 12
HV regular appointment, she saw how well he was (playing with gym) and agreed that he didn't seem to be bothered by it.
Day 13
My 6 week check. Asked different GP because I'd forgotten to ask the first one, if there was any point at which we should begin to worry and bring him in even if he was otherwise well (feeding, wet nappies, passing wind, calm and relaxed, not vomiting). She said no.
Day 16
Wolfcub waits until DH had gone back to work after long weekend off. There's a little strain, and I massage his tummy and cycle his legs (I did this to soothe him, I think he'd have managed without) and he fills his nappy at last. It isn't hard at all, maybe a little pastier than his newborn ones, and more orangey (Tikka Masala rather than Korma... ) and it stayed within the confines of his nappy! (Though I did manage to mess his clothes up when I cleaned him up.
After the 16 day marathon, he went 6 days, then 4 days, then 7 days (that was 2 days ago and its the first one to escape the nappy... and filled one leg of his sleep suit!). The last couple have been back to more yellowish but I don't know if there was a significance to the colour.
We haven't done any of the remedies, just held our nerve after he had had his tummy given a clean bill of health. He hasn't been constipated with solid stools as such, he's just been taking his time.
On a less happy note, he's managed to avoid doing any of them whilst DH has been home, so he hasn't done a dirty nappy since he went back to work at 5 weeks even though his son is 9 weeks old and he's in charge of most evening and weekend nappy changes!