The back of my tongue is swollen and its very painful to move,talk,or even swallow. its been like that for a few days now. what's wrong?

Need to examine: It is not feasible to provide a meaningful opinion without taking additional history, physical examination and may be some tests. It would be prudent to see your doctor ASAP.

Need examination: You may FEEL as if it's the "back" of your tongue when in fact, it is more likely the upper portion of the pharynx. You need for a doctor to look into your throat and likely get a culture to make sure there's no strep or possibly viral infection such as mono. Consider yourself contagious until you get this checked out. Visit any Urgent Care or Fast Track ER but don't wait.

Glossitis: Glossitis can mean soreness of the tongue, or more usually inflammation with depapillation of the dorsal surface of the tongue. It may be due to infection of some sort. If it does not resolve, then see the Dr. Best wishes.

Swollen tongue: Do you have a fever; have you been ill; did you sustain an injury or a burn; did you have an allergic reaction? This is impossible to diagnose accurately without additional information and a clinical/visual examination. Call your dentist or an ENT specialist for an appoinment for an examination.