Brief Answer:
Gastric pain.

Detailed Answer:
Hello,
Thanks for asking query on HCM.

I have read your details and i appreciate your concerns.
Most likely your symptoms are due to acute gastritis overlapping with dyspepsia.

Inflammation of the stomach is also known as acute gastritis. When foods enter into injured areas of the stomach, the stomach lining and the interior walls slow or stop altogether the flow of blood in the stomach walls, causing reddening, irritation, and in some cases bleeding. All of this can gradually lead to chronic ulcers. PAIN after eating is highly suggestive of ulcers in stomach.In lay mans language when you eat food parietal cells in stomach secrete large amount of acid.This acid irritates the ulcers in stomach hence cause pain.
Retrosternal chest pain especially after eating meals involving rubs and sternum are highly specific for gastritis and acid reflux.
As cardiac investigations are normal endoscopy should be done to rule out gastric ulcers with overlapping infection with bacterium H.Pylori.
Dyspepsia, in layman's language is known as indigestion. It is a term that describes discomfort or pain in the upper abdomen. However, it's not a disease in itself. Dyspepsia is a group of symptoms which often include bloating, nausea and heartburn.

As the onset in your case is acute.Most likely cause of indigestion is due to either overeating or taking over oily or fatty food. Anxiety or smoking or aerated beverages can also cause the symptoms.Bloating and acid can be caused by any kind of food. In most of the cases, it's fatty foods which cause these symptoms. Any food whether it's fat or protein or complex carbohydrate when can not be properly digested, releases large amount of gases like hydrogen, methane, carbon dioxide which causes burping.


Treatment
Take a proton pump inhibitor like Omeprazole 40 mg once daily.It would inhibit secretion of acid in stomach hence would help relieving the pain.

Before taking food take two table spoon of antacid with half cup of water it would form a protective covering over stomach and would prevent acid from irritating the mucosa.
Apart from this, some dietary restrictions are to be followed-

- Avoid alcohol or smoking.
- No aerated beverages.
- Take light non spicy easily digestible food for few days.
- No Fast food like pizza or burger should be taken.
- Drink a cup of cold milk daily.
- Avoid fatty foods.

Hope I've answered your query.
Feel free to ask any follow up questions.

---