As someone who has BTDT, I would try to nurse Dc3, but if for some reason Dc cannot nurse well, then give yourself permission to not pump at all, pump for a limited time, or only pump part-time and supplement from the start. I have nursed successfully and also had to exclusively pump for my babies. They were each so very, very different. My first two were early like yours and too small or tired or uncoordinated to nurse. I worked for 6 months to get Ds1 nursing but by 6 weeks I was exclusively pumping with Ds2 (eventually we had to supplement then switch to formula). I have no regrets and know that Ds2 would really never have learned to nurse so I was glad that I hadn't made us crazy trying. That said, pumping full time is hard and time consuming. I knew that I wanted to avoid that if I could.
My third was full term and that made a HUGE difference in his nursing abilities. He was by far the easiest to nurse. I did need help from the LC at the hospital but that was enough. I had decided ahead of Ds3 that I would try to nurse with the following limits: try for up to 4 weeks and with up to 3 LC visits, then I gave myself permission to just let go. If nursing didn't work or needed more support that that, I planned to pump part-time for 3 months but not feel guilty over formula if we needed to supplement sooner. At 3 months I would re-evaluate if pumping was working for me/our family, how formula was working, etc.
Ds1 (2006). Ds2 (2010). Ds3 (2012).