To be honest, it sounds like you'll be fine, he must have been getting something in those first days to wee and poo like that. If he was born on Tuesday, and meconium passed by Thursday or Friday, that is fine! Robyn was born Thursday, on Sunday she was still passing meconium transition poops, on Monday she stopped going at all (wee or poo), and they gave me the rest of Monday to get her feeding, before insisting on top ups (I started expressing for her then). But she was term (37+6) so I don't know if that makes a difference with how long they'll leave a baby who is losing weight?
Like I said before, get stimulating your supply and work on dropping the top ups. If you have to top up because LO is hungry and frustrated at the breast, give just enough to calm him before putting him back to the breast. You should find that soon LO will feed for longer before needing a top up, and will need less top up to settle. It might help to keep a log of how much he's taking each time (and if you pump, how much you get) so you can see if the top ups are indeed getting less.
Good luck
Like I said before, get stimulating your supply and work on dropping the top ups. If you have to top up because LO is hungry and frustrated at the breast, give just enough to calm him before putting him back to the breast. You should find that soon LO will feed for longer before needing a top up, and will need less top up to settle. It might help to keep a log of how much he's taking each time (and if you pump, how much you get) so you can see if the top ups are indeed getting less.
Good luck