Thin bones, low weight, digestion problem

Patient: I am 24 male and 5.4. I have just 45kg weight. my bones are very thin, I cannot stand for longer hours because my back starts hurting. Most of the times I also feel bloated, cannot eat even if my body needs. how can I recover from this condition.

Symptoms: Shades below my eyes, bones are very thin, weight is just 45kg. digestion system is not well