Talk to Gastroenterologist on Hunger Issue

Kindly guide me about these issue or to whom should I consult? 1. Hunger episodes: Few week I eat well with normal hunger schedule but then more often I feel like my stomach is full. Even If I'm hungry I could hardly eat half meal. Or to skip lunch etc. 2. Hard to get weight. As I'm under weight 3. Dullness 4. One nail become pitted after every few months