Bummed and need to vent

Since my son was born I never was able to produce enough milk...he was underweight his entire first month until the dr finally said to supplement with formula. That was a blow. Then about 2 months later he stopped nursing so I had to pump the little milk I had for months and months now. He used to get about half milk, half formula for his daily feedings. But now that he’s getting bigger I can’t keep up and he only gets about a a third milk, 2/3s formula for his daily intake. I just tried feeding him my 5oz milk (from morning pump) when I put him down to nap and he finished it so fast and cried immediately for more. I had to rush downstairs to make a formula bottle and by the time I got upstairs again he had cried himself to sleep.

I feel awful. I know fed is best but today I’m struggling with anger at my body for not doing what it’s supposed to do for my baby.