Going back to breastfeeding

My LO had serious issues with latching early on. He would immediately start screaming and refuse to take to my breasts. After hours and hours of screaming and a seriously hungry baby refusing to eat, we switched him over to formula. I've continued pumping but don't have much of a supply. I'm pumping about 5oz a day now at 5 weeks pp. Well today, for some reason, I decided to try to see if he would latch and breastfeed. Well he did. I had hoped after he got a little bigger he might do so, and he did. He latched on and nursed for half an hour. I don't know how much milk he got. Anyways, do you have any advice on how to go about getting him to breastfeed now? I'm okay with supplementing if I can't produce enough to cover 100% of his feeds, but I would like to get to maybe nursing half the time if possible. Any help?