Hello doctor! I am really upset due to my weight....

medication to gain weight :
- there is some simple medication that can increase your appetite thus increasing your weight such as :
1. Dronabinol 
2. Megestrol 
3. Oxandrolone
- first consult your doctor before taking any of those medications 
Increase appetite medications side effects :
1. nausea and vomiting 
2. dizziness
3. stomach discomfort 
4. changes in mood 
5. nerviousness
6. increase heart rate 
Vitamins that help with increase weight ?
1. vitamin C 
2. vitamin B1 / B6
3. vitamin A
general advices :
1. consult a nutritionist to guide into a better and suitable diet
2. drink more fluids 
3. make sure that your diet contain plenty of health calories
4. pay attention to dinner meal and dont miss it
5. make sure that you are not taking any medication causes weight loss as a side effect
6. exercise
7. avoid stress and anxiaty 
Causes of weight loss :
1. unhealthy diet 
2. smoking
3. stress
4. medication side effects 
5. chornic diesease