My boy has dropped from 75th percentile to almost 50th, now 20 weeks, and other bf mums have had the same and tell me.its completely normal. Do yih mean losing weight or percentile? They said they're babies caught back up once they started weaning. I started weaning at 18/19 weeks after a consultant at hospital recommended it. We were there for a suspected cows milk allergy follow up as I was combi feeding but I believe it is a foremilk hind milk imbalance as my lo has always fallen asleep at the breast and no amount of tickling will keep him awake. I have begun to express with an electric pump just this week so I can switch to bottle feeding expressed milk to ensure he gets the hind milk. So far we have only expressed enough to make porridge with but I am already seeing a huge difference! We buy organix porridge as its wheat and gluten free.