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Thanks for contacting with your health concern
1. After going through your symptoms there is the presence of swallowing disorder [dysphagia] due to which you are having the problem with eating for which a consultation with a Gastroenterologist is of utmost important [even if you are afraid] since you have unintentional 
weight loss, gagging/choking during eating.
2. the cause could range from 
movement disorder of 
esophagus [esophageal spasm, achalasia], GERD, gastric ulcer, neurogenerative disorder [Parkinson], along with 
neuromuscular disorder like 
myasthenia gravis, multiple sclerosis
PS. check with the exhaustive list with your attending physician.
3. keep in mind that since you are not been able to eat, it will result in:
- dehydration
- poor health due to inadequate nutrition [malnutrition]
- risk of fluid/food entering the trachea and may cause 
pneumonia.
4. If pain and dysphagia do not subside refer for oesophagoscopy and barium swallow, upper GI endoscopy and if investigations confirm there is definite and progressive obstruction then refer for urgent indirect 
laryngoscopy.
5. There are various treatment of swallowing disorders ranging from dietary and lifestyle modifications to Medications & Surgery. Your doctor will recommend the best treatment for you depending on what causes your disorder and symptoms, till then:
- bland and soft diet, more of milk
- avoid hot drinks and spicy food
- do not lie down immediately after food. take small, nonbulky meals.
- head high position at night.