probably an acid issue but stress can make that worse. This will sound strange but bear with me - raise the head of your bed by putting thick books or blocks of wood underneath. Ideally this would be about 6 inches but it takes a while to get used to it and 4 will help quite a bit. This means that gravity is helping to keep the acid in your stomach at night.
You must avoid ALL fizzy drinks, especially in the evening, and no alcohol. Make sure you stay upright after eating and have small frequent meals. Dont eat late at night.
To help with the stress of exams get a magnesium oil spray or buy epsom salts, put 500gms in a warm bath, soak for 15 minutes and pat (not rub) dry. You will absorb the magnesium through your skin.
You may also have a virus as your glands are swollen but acid can cause this too and once you are able to eat normally you'll probably shake that off.
What medication are you on? This should fix the problem in a week with gradual improvement before then,