Great responses so far. If you are determined to make this work (if you truely want to breastfeed your baby), you need to RELAX about the whole thing! Stay in bed for a day (or in your jammies around the house, on the couch or wherever) and just nurse when she seems like she's hungry. Lip smacking is a good clue or rooting like she is trying to find a breast (on anyone). Try laying down on your side facing her (can be hard, I couldn't master this for 3 months!) or put the pillow on your side and nurse her in the football hold with her feet under your armpit. You have to be relaxed to let the milk flow, make a nursing area (glider, or a certain chair) with a place for your water, snacks, a good book, the tv remote... Just sit there and ignore all the other things you'd like to be doing like cleaning the house or working on whatever. Your sole job for the next 3 months (at least!) should be to take care of your baby and meet her needs. :)
Get someone else to clean your house! Ask friends to bring you food if they ask what you need! Maybe with the pressure off, you can relax enough to make this work!
That said, I will second what someone else said that your baby could be allergic to something you are eating. Mine was allergic to dairy. That means YOU need to stop eating dairy! That is actually one of the most common allergies in babies, so without a Dr diagnosing it, you can elliminate all dairy from your diet and see if she eats better and stops spitting up. She may be spitting up because she is anxious for the milk to come in and is sucking down too much air before you let down. But she could be allergic. Substitute soy milk for regular milk (costco has it cheap) and the Vanilla flavor is sweet. Stop eating cheese, yogurt, and ice cream, too. If this works and she eats better you can find soy versions of these if they are part of your normal diet and you would miss them! That is worth a try!
Plus, you should ALWAYS have a water bottle in your hand, especially while you are nursing! Keep hydrated and keep the body making milk! Eat healthy and if your husband wants to help when you are nursing, have him bring you water and food. It is perfectly ok to snack all day as long as it's not junk, because you are feeding 2 still and need the extra calories like when you were pregnant. Plan on doing this as long as you are nursing!
Your hubby doesn't really need to get up with you during the night. At least someone could be rested. Let your baby sleep with you too! Best thing I ever did! It makes nursing on demand so easy. Don't listen to what anyone says and try it. If she gets fed when she's hungry, she may even sleep longer, but either way at least you are not fully waking up each time.
If it is painful, she may have a bad latch. That can really ruin it for you! Make sure her upper lip is not tucked under, you can pull it up if you can't see it and make sure she looks like a fish. That is usually how you can tell a bad latch.
I hope you get the answers you need. I wholy support breastfeeding as it leads to healthier babies and a healthier society on the whole. I wish you the best! Now go enjoy motherhood!