Feeling defeated

I want more than anything to breastfeed my baby. We had to start supplementing formula because I am not producing near enough and my baby lost 10% of her birth weight and was having low blood sugars. She was already growth restricted so even a little weight loss is big for her. I am latching her as much as I can but since we introduced the bottle she only sometimes will latch. I am pumping every time she eats and I usually only get 20-30 mls combined. I am so emotional because I want this so badly.