My baby hasnt grown in 5 months?

Went to doc in feb she was 16lbs went to doc other day baby was 16lbs BUT she had just drank an 8 oz bottle so if anything she lost a few oz. she drinks bottles all the times eats good 4 times a day chicken fruits and veggies. shes in the 5th percentille. she hasnt grown either, doc said hes running tests on her in 2 months if she doesnt gain 2 lbs in that time. something about malabosorbation promlems? liver, pancereas? i couldnt concentrate i was pretty bothered by this im so sick of ppl bringing up that she so tiny and doesnt look anything like a 10month old, its true. she has almost no meat on her. she seems to be develping normal. what is the doc talking about what he said to me what does this mean what happens ?