Can't stop crying over my milk

My son is 9 days old. At his 48 hour app we were told he lost more weight than considered acceptable and I was advised to start supplementing with formula. My nipples are flat and low so latching has been an issue since the beginning. It didn't bother me that I couldn't breast feed bc I knew pumping was a good alternative. Well after a few days of monitoring his feeds, I'm finding the breast milk feeds are not substantial enough. I struggle to pump more than an ounce and a bit and I can see that when my milk seperates, it's has barely any of the thick good quality milk. My milk is useless and im so sad about it. I feel so guilty. This sucks. He gets so gassy with the formula, which adds to my guilt. Ugh just feel so sad.