I have a colleague who can only pump one oz. breast milk each day. She still give it to her son and add formula until 5.5 months when her milk supply gradually stopped. This still manage to keep her son sick-free for 10 months. He only got 玫瑰疹, which is a common but mild sickness for babies. Now her son has passed his 1st birthday and still in very good health and in big size.
So you see, even a little works a lot! Keep it up! Feed direct as much as you can to stimulate your supply. We all support you. .