Earlier, i felt like i had to burp. when i tried to burp, it turned into about to throw up. when i tried to prevent myself from throwing up on my desk, i started coughing, and now my throat is burning. i also had phlegm. what do you think happened?

Stomach acid, mucous: The stomach contains many different digestive enzymes, & hydrochloric acid (which can cause the burning sensation) & mucous (which can sometimes look like phlegm). When you burped, some of the stomach contents probably came up which made you feel like vomiting - you managed to stop that, but the acid irritated the lining of your throat - causing local irritation, causing mucous production.