Hi, the problem you are complaining of is due to severe hyperacidity and acid reflux.
Since you are complaining of vomiting every time you drink water, you might become dehydrated. You are also complaining of frequent loose motions, weight loss and all the problems are going on for a long time.
Next Steps
You must be thoroughly investigated to rule out any allergy or pathological conditions like Celiac disease etc.
Health Tips
Homeopathy has wonderful treatment for such problems. To consult me personaly please contact through this platform.