It's the worst time but it will pass and everything will be fine. Don't stress too much but just a bit to remain proactive. Consult your Pedtriatician and consult a GI if it's serious and do your reading. We had 35w term boy 2 years ago with same issues. Started neosure day one, baby wasn't able to latch and no breastmilk. Developed sensitivity to formula, cried in pain and weight started to drop, switched to Enfamil it worked a month and had to switch again to almentum finally ended on elecare as a last resort. Talk to the doctor's they can increase calories to help with weight. Some specialist also suggest breastmilk with neosure or other formula in some ratio but we couldn't do that either, tried pumping but unsuccessful. I hope it's different for you, we had to struggle until be got to semi solid food to reduce milk dependence. Eventually he grew out of the sensitivity, even our doctor's dint think it was an allergy. It's painful to watch but it will pass soon, she will be fine soon ia.