My son, also a preemie, did not sleep through the night for a looong time.
He got up every 3 hours for a bottle for a long time. Little bellies get hungry.
I had him in his cradle propped up on a step next to me in the living room or bedroom for months. I even propped up his crib mattress when he slept in there by placing a pillow under the mattress.
People told me to sleep when the baby slept so I did. I would go right back to bed & pass out. I didn't have much help so I was very sleep deprived forever. I'm sorry you are going through this. I know it's tough to be sleep deprived. If anyone else is there to take over a feeding or two, let them. My baby didn't sleep through the night until he was a year and a half but might go to 5 or 6 hr stretches. But don't worry, every baby is different.
So hang in there. Try to take it one day at a time. It will end soon. I promise. Take help when you can. Rest/sleep when you can (when baby sleeps). Let everything else fall by the wayside for right now. Laundry or housecleaning can wait for now. You are doing a great thing for your little one. This too shall pass. You just have to see what you can do on a daily basis to cope. Hang in there honey!
Edit: one thing to add......the "dream feed" someone mentioned saved my life. Right before we went to bed at 11pm, I'd pick him up from his bassinet lightly & quietly, change his daiper gingerly so as not to wake him & give him a bottle in his sleep. He was still asleep but I'd put the bottle to his lips and you'd be surprised........they take it. So amazing. This helped me get a stretch of sleep at that time so even if he woke at that age it might not be until 4 or 5am instead of at 2am That helped greatly.
Make sure he's warm. Mine stopped liking the swaddle at this age. He'd just wiggle out of it so I'd make sure his jammies were warm enough for the cooler weather.