Baby's not gaining enough weight

As some of you may already know, Julius has not been gaining enough weight. He is not doing well with feedings. He keeps pulling away. I have tried herbal supplements to encourage lactation, but unfortunately, it ended up giving me mastitus. I am not sure why Julius is not feeding well, but will you pray that it will get better. I believe I am producing enough milk, but he seems to get frustrated when he feeds. I just fed him 4 oz of formula after he breast fed for about 20 minutes. He gulped it all down and his now-frequent fussiness was gone. Anyway, please pray for wisdom for Lumuli and I. It's tough to think that I would have to be done with breast-feeding, but if need be, I will. Anyway, I'll keep you posted.