I've had a cold for a few days. today i have been nauseous and have a dull pain right below my sternum and also have been burping. what could it be?

Reflux?: sometimes when you have a cold, and are experiencing PND, mucous draining down the back of your throat, you can experience gastritis, acid indigestion. could try an acid blocker like pepcid (famotidine) and avoid spicy food and carbonated beverages

Stomach flu: All your symptoms may be part of a viral illness, sometimes called Stomach flu. Avoid food for a day or so, drink clear water or electrolyte solution when nausea has subsided and advance diet slowly after that as tolerated. If start vomiting, seek medical help to avoid dehydration.Feel better:)