Another question: how do we proceed or is this normal?

Another question: how do we proceed or is this normal? We've been at it for almost two months now, and we still eat 70 ml of formula every three hours, he seems full but I know that's not much for our age, he's mostly not eating anymore. We gained 750 grams in the first month, they said that was normal, but now it seems like he's lost weight, maybe it happens to others too.