Baby only wants 2 oz bottles

Hey guys! My little one is 9 weeks. At our 2 month check up his weight had dropped from 40% down to 12%. He was sick with rsv which caused him to lose weight, but ever since then he would be completely happy to take 2 oz every 3 hours. I struggle to get 18 oz into him. He does have reflux which we started him on meds last week but that doesn’t seem to have made a difference at all, still spits up some and coughs. He has just breast milk and I’ve migrated toward mostly bottle feeding bc i have to try and monitor how much he’s getting.

Anyone have similar stories? How did you get your kiddo to eat more? I have to wake him up every three hours to eat! He’s perfectly content and happy.

Anyone have to fortify their breastmilk to get more calories in your kiddo because they just don’t care to eat more?

Worried mom over here!