Has anyone else baby had a weight problem when they were a baby my daughter was 8lbs at birth and…

Has anyone else baby had a weight problem when they were a baby my daughter was 8lbs at birth and lost weight went down to 7lbs 10oz then started going back up now my daughter is 3 months old now and is 9lbs 12oz she is gaining it but not very fast very slowly and they are worried so they told me to put otmeal cereal in her formula bottle to thicken it!