Your situation was very similar to mine. My baby was 5lb when she was born, was yellow and needed to shine light in hospital. She kept on falling asleep while feeding, took almost 1 hour to feed, then wakes up every 1 - 3 hours for feeding, my breasts were painful and injured because of her biting, and to make things worse my family kept complaining that I should just give up and use milk powder. My milk supply did not come in after 4 - 5 days, and I just continued to feed her with breastmilk only.
I suppose I was stubborn and I was worried that if I gave her formula too soon I may not have enough milk (because if baby feeds less often, I will have less milk) and she may refuse my milk. Anyway, I gave her some formula until day 4 -5 .
But when I went to health clinic about 1 week after birth, they said she was a bit yellow but not bad enough so she did not need treatment and her weight gain was satisfactory. They also checked my breastfeeding technique and taught me what to do about the painful breasts. I was glad that I visited them early.
By the way, I had exactly the same experience. In hospital the nurse told us only to spend 10 minutes on the breast and then gave milk powder. I did my own reading homework and knew that they were wrong in their facts - newborn babies can take a long time to feed, and we should not limit their feeding time. I think it's also because the hospital is short staffed and they don't have the time to 'wait' for mums to feed for an entire hour. Also, we should let the baby finish drinking from 1 breast before changing to the other side, and not watch the clock and switch every 10 - 15 minutes. This is to ensure your baby finishes the richer hindmilk which contains more calories and fills up your babies for longer.
My conclusion is, bring your baby for check-up early, and ask for advice regarding your feeding technique make sure it is correct and baby is able to drink milk directly from the breast properly. If your diaper count is not enough, you need to make sure it's not because of poor feeding technique. Because poor technique, means baby's not getting enough milk and your breasts are not well stimulated to produce more milk.
You can always walk in or request them to bring forward the appointment. Babies do take a long time to feed in the beginning and it's not easy especially when you're just starting to produce milk.
But try to relax and have confidence , let your baby drink as much as they like. If your baby's supplemented with milk powder, still try to pump out your milk more often every 2 - 3 hours to boost supply. Eventually your milk supply will increase according to your baby's needs, and as your baby gets older s/he will drink so much faster. This will make your life easier as well.