Thanks guys! Similac Sensitive seems to have done the trick! He is doing much better nursing, although he falls asleep quickly and nurses a long time and is still hungry...sooo still suplimenting....he's a little piggy!

My daughter would spit up breastmilk and formula. Although, it did seem that she would spit up formula more often and she also had tummy aches and gas with formula. The pediatrician recommended Similac Sensitive. She's been on it for about 2 1/2 months and is doing so much better. She doesn't have very many tummy aches or spit ups.

I never produced enough either, even with pumping like crazy. Miles' had bloody stools @ 2-3 weeks, which meant milk protein allergy, so we switched him to soy, and I don't each much dairy anyway. Josh had respiratory issues (mucous build up in throat), which we thought might be due to reflux, then thought environmental, but we switched him to soy as well and it cleared up. He spit up/threw up the soy for the first week while he adjusted, so we tried different brands, and now he's fine with it.
The problems could be a manifestation of milk protein allergy. If you don't drink a lot of dairy or eat a lot of cheese, he won't get much milk protein from you, so it could be an intolerance of milk protein in the formula.
Keep having him elevated after feeding, and try to minmize movement/activity after feedings. Hope it helps!!!

Good luck with the nursing, pumping, and feeding. It is a lot of work, and you are a rock star mom for doing it. I hope he starts nursing more enthusiastically once he gets a bit older.
I had similar problems with pumping. It sucks, literally. There are other women on the boards who pumped successfully for a long time who might have better advice.

Thanks guys! I would love to strictly nurse, however he doesn't respond to that much right now....he's getting better, but to ensure his growth the NICU and lactation consultants have told me and are telling me to continue to introduce him a few times a day and not to give up. Pumping is all I can do right now and it takes an hour to get about 2 1/2 to 3 ounces with a great pump. Not giving up yet, but feeling really really tired in the process.

Good news is, he didn't spit up last night, but was up with a great deal of belly aches and seems to still be suffering from it now....yet he's only had breast milk (I've been pumping every extra minute I can, just to get even a drip extra for him). Fingers crossed and lots of prayers this pans out soon! Thanks!

Seconding Trish's suggestion to try a slower flow nipple. Good luck building your supply if you decide to try exclusively breast feeding. There are a lot of threads here on how to do it.
We ended up on formula, and my daughter was what the doctor called a "happy spitter". She spit up after every bottle, sometimes a lot. She still grew very quickly and stayed healthy. She didn't spit up breast milk, but that was because she never got enough to spit up from me. Your case sounds a bit different. Don't hit the panic button just yet - your son might just be a spitter. My daughter didn't really hit her spitting up stride until 4-5 weeks. She didn't stop spitting until she was easily sitting on her own.

It's possible he's drinking the FF faster that the BM feeds & can't handle it. Maybe a slower flow nipple would help? If it's possible to BF more often than I second Patty on trying to cut out the FF completely. (((HUGS)))

I would just cut out the formula and try to strictly nurse. The formula is not doing any good if he is just spitting it back up. Breastfeeding works on a supply and demand premise if you add in some extra feedings your supply should increase. Just watch for wet and dirty diapers for a few days to make sure you are producing enough and watch his weight gain. You can also try to add in extra pumpings to build up your supply and also feed the milk you pump in place of the formula.

some babies stomach just cant handle formla my oldest couldnt and we had to switch formla every week for about two months til we found out she is lactose intalorinte i would just keep tryin formalas good luck and i hope he stops throwing it up

Do you drink milk or eat any dairy products?