Heartburn and Indigestion:

Heartburn is a term used to describe a burning sensation occurring in the chest area (heartburn has nothing to do with the heart itself), which may also be accompanied by other symptoms including: regurgitation, a bitter taste at the back of the mouth or throat, excess salivation, belching, and difficulty or pain when swallowing.  Also called acid reflux disease.
There is often a feeling of fullness after eating, feeling sick and vomiting. 
Heartburn can develop at any time and may not always be as a result of eating or drinking.

Again, stress is a common cause, but your doctor may conduct a test for the presence of Helicobacter pylori bacteria in your digestive system and if confirmed you should be prescribed antibiotics. The advice for sufferers of constant heartburn and indigestion is to eat slowly and in a relaxed environment; concentrate on enjoying your food and chew it thoroughly. Don't drink too much whilst eating.  Sip fennel, mint, apple or camomile tea.  Stop smoking!
Digestive enzymes and probiotics are also helpful.

Foods to avoid include crisps, chips, nuts and rich, creamy or fried foods; acidic foods like vinegar and pickles; some raw vegetables; some citrus fruits or unripe fruit which can cause acid reflex.