Op, how tough
it sounds like your baby is being very well looked after.
I have experience of an early baby and expressing colostrum while they’re under the UV for several days.
Firstly (and something you don’t read on here enough) your body needs rest, food and hydration to be able to produce colostrum/milk. Are you able to get a good chunk of unbroken sleep somewhere? I know how noisy postnatal wards are. I know you won’t feel like eating and drinking but please do both as much as possible.
I know it’s controversial advice, but I would suggest giving baby some formula and giving yourself 12 hours off to recover, have a good sleep, a meal and get your fluids up. You don’t need to express colostrum for your milk to come in, and it sounds like that will happen in a day or two, so now is your chance to break the exhaustion/fruitless pumping cycle. Stress will certainly affect your production.
From tomorrow afternoon or so, start using a double hospital pump if they have one.
The above really worked for me, and we had a really good breastfeeding experience after that. You may need to pump for a week or two until baby puts on a bit of weight and feels energetic enough to feed for themselves, but don’t panic.
Congrats on your new arrival 