My body is like shrinking no matter what I eat

I suffer from theses symptoms from my childhood probably. I am 21 now. I have gone to various doctors but none could help me. I eat a lot and nothing of outside. No oily, fried, spicy food. And I don't have fast metabolism.

Symptoms-

1. General weakness

2. No growth in stamina

3. Very thin wrists and lower leg.

4. Pain in lower legs

4. In winters, legs and especially Hands get cold and white.

5. Hair are dry and breaks a lot, skin is also dull and dry.

6. No weight and Height growth since 4-5 years

7. I can see my lungs.

8. My buttock is flat and sitting makes it pain.

8. I go to toilet 3 times a day but sometimes it is 3 times in the morning and 2-3 times later in the day.

Why is that my body doesn't extract nutrition from the food I eat? Its like I eat, body extract energy for survival and it gets out. No growth.. As if my body is shrinking