Breastfeeding problem

I got mastitis (a breast infection) because Isaac went a whole night where he hardly ate, which caused a clogged milk duct that got infected. It hurts a little, but the flu symptoms (high fever and body aches) were the worst part. The medication made the flu symptoms go away, but then my milk supply plummeted last night. He breastfed off and on for three hours, trying to get enough to fill himself up, and we finally had to give him formula. He was so hungry. I thought I would have to wean him at 5 weeks.

My milk seems to have come back in this morning, but now he is barely eating. I'm sorta stressing out.