My preemie struggled to drink from breast too. I had lactation experts sit with me for hours and my technique is fine. Baby latches, but does not drink much, and I am not comfortable letting my below 1st centile baby go without, because of some practitioners' obsession with breastfeeding directly from the nipple. We did not have a standard baby, and my baby is not necessarily doing things regular full term and average weight babies do. I work with the baby I have, and the limitations baby has, not some ideal of how things 'should' be. By all means get some advise first, but don't beat yourself up if it doesn't work for your baby.
I have been pumping and bottle feeding for almost four months now. Baby is now almost 8 pounds, and was born below 3 pounds. It is a time-consuming and relentless business. I would suggest trying baby on breast and then pumping afterwards to empty what remains in your breast, and use that as a top-up for the next feed, if baby has not latched/drunk enough. Then repeat. Sometimes I just go for the expressed milk bottle, and don't do breast first.
When it comes to building supply, try to have a pumping holiday this weekend, where you pump every 1 hr or so. Just demanding, demanding, demanding, and your body should rise to the challenge. It will slowly start producing more. Get a hospital grade pump. I prefer the Medela one, which you can rent for around 50 quid a month. Worth every penny, as it really gets the milk out. I tried other ones, but this one worked best.
When you pump, keep going for another few minutes after milk stops flowing. Massage your breasts during pumping. Pumping after a shower helps, too. People also suggest eating oats and having breast milk supporting tea. Drink plenty, as it makes a difference if you are dehydrated. Pump both breasts at the same time.
What I realised is that after 5 hrs sleep at night, I get a big morning supply, which covers two and sometimes three feeds worth. This was a total game changer. This supply I use for the next night, where my partner takes care of two feeds, so I get some sleep. This system really works for us. I am now switching/going to bed at 6AM after the night shift, while he now wakes and takes care of the coming 5/6 hours, while WFH, with the milk I pumped after last night's sleep. It has kept me sane and this system sustainable. If you partner does not WFH, perhaps doing this in the early evening could work, when partner comes back from work.
Don't hesitate if you need a few supplementary formula feeds to keep you going. If you had a low birth weight or preemie, baby there is special formula on prescription, you could ask your midwife or NNU about.
In the end, just try your best. All baby's buddies from NNU are having different feeding regimes now. They are all growing and nobody gives any other mum a bad time. In the end, fed is best.