We need to understand your digestive health first. Lot of the weight issues depends on our Gut health.
Although there is possibility that your genetic make up is of being underweight, there can be other lifestyle concerns (not medical) for your sever lower weight for height. Lifestyle means stress, sleep, diet and exercise something must be imbalanced for such lower weight.
For the height 5.6ft we want 65 to 70kg weight for good health. But 38kgs means your BMI is 13 which is an indicator of severe malnutrition and it's very urgent for you to get help from Dietitian and Doctor.
This low body mass can cause you to:
1. Feel tired
2. Low bone density
3. Anemia - iron & other nutrient deficiencies
4. Low immunity
To mention a few health issues of low body weight. I can only recommend you to meet your consultant as early as possible...
Next Steps
You can connect with me to talk more about your health and I can help you with your low body weight solutions