Tonight has been REALLY rough with feeding! For 2 straight hours, LO screamed to feed but then fell asleep soon after starting (even with using a diaper change to wake her up), but would scream again as soon as I laid her back down! She has been cluster feeding a lot, and I'm afraid she wasn't able to get enough!!

She will not take formula (the doctor had us try when she was losing weight at first). I feel horrible that I apparently am not providing enough for her tonight!! She is asleep now (we'll see how long that lasts), and maybe her being tired was part of it (she was awake a lot more than usual during the day today), but I'm afraid she has fallen asleep hungry. Any suggestions on what to do when LO is hungry but the well seems dry???
Re: BFing woes...
Ditto PP, we also did lots of nighttime cluster feeding in the beginning. What finally helped us, was preemptively cluster feeding her in the early evening. It took a while to work up to it, but now we nurse at 5,7, & 9 and then she'll STTN.
Hang in there it gets better and is so worth it!
My DS did this for a little while around the same time... I used to try and get him to suck on my finger first (I have no idea why, but he would take that and not my boob) which would calm him down and then I had to "trick" him into taking my breast and then he was fine.
Also, is you LO doing this around the same time every night?? If so, try getting her to feed just before that time. So say she normally gets fussy around 7pm, try feeding her at 6:45 or 6:30.
One thing that helped me a TON was setting an alarm! DS used to go to sleep at about 9-10pm, wake at 2ish to eat, go back to sleep, wake at 5ish, go back to sleep, and then wake again at 8ish. I'd set my alarm every night for 2am, 5am, and 8am. When that alarm went off, sure enough DS was rooting in his sleep! So I'd just pick him up, feed him, and put him right back down when he was done! Most of the time he never even woke up! If you know about what time your LO wakes up to feed at night, set an alarm for about 15 minutes before that time and try to get her to feed then. Doing that seriously saved my life!
HTH! GL!!!
I know it's rough in the beginning but it will get better. Don't automatically assume that you have a low supply just because she is screaming and feeding on and off for awhile. I have plenty of milk (an oversupply of about 9 ounces a day) and LO still has her moments of screaming and going on and off the breast. For instance, tonight it took me 2 hours to get her to go to sleep for the night and she was screaming and didn't seem to like the breast. It turns out she had a huge poop in her belly. Once it was out, she still wasn't totally interested in feeding for another half hour. She was going on and off and crying a bit. I don't know what bothered her that time but she eventually fed and went to sleep.
Your LO may just want to be held and suck for comfort. They go through phases where their needs change. Try to stay away from the formula as you will have to pump to make up that feeding and the pump doesn't work as well as just feeding the baby.
I promise it gets easier. I was thinking tonight how happy I was that I was BF since I would have likely wasted a bottle of milk when I thought she wanted to eat all that time. Hang in there.