Supplementing with formula - starting at 7 months old

I have EBF up until now and my son is almost 7 months old. His weight tanked at our last checkup and he is 2% now. He isn’t napping great and waking 3-5 times a night and I’m starting to think he just isn’t getting enough food - and I’m exhausted. I do homemade purées about 2x a day and I’m thinking of giving him a bottle of formula and I feel heartbroken. I made it to 14 month breastfeeding with my now 2 year old daughter and she never had formula. What brands are good and how do you go about supplementing and still mostly nurse him? Why do I feel so terrible about giving my kid formula- ugh society! Any helpful thoughts?