Dr, My Six Months Old Baby Is Drinking Milk Only

Dr, my six months old baby is drinking milk only when asleep that too 2 oz. In one day she takes 50 oz. From fourth month she refused breast and i gave her expressed milk in bottle. Now due to low supply i mix formula milk. Breastmilk or formula she drinks 2 oz only. She is interested in solids so i mix cereal with formula. She is active but not gaining weight, now 6 kg only. She used to spit out after drinking milk. Ped prescribed cypzest to increase appetite but not improved. I m so stressed out pls suggest any remedy.