baby won't eat/ bloated

My daughter's stomach looks like its about to explode! Its so big and bloated. Her skin is tight and stretching. She normally eats 2.5 every 3 hours... She only took .5 oz when I tried to feed her. Now it has been 5 hours since her last feed. I have tried massaging her belly and moving her legs like riding a bicycle, prune juice and even a supository since its been a while since her last poo... I'm running out if options and getting scared. What do I do? (Born 26 weeks, now 40.)