Since the antibiotics didn't help, you're probably up against a virus. As andreja said, there could be a wide range of viruses that would cause these symptoms, including the flu. I would recommend having your doctor run mono/EBV tests, as well as any other typical viral tests he/she thinks deserve merit. Good luck!
It sounds like the antibiotics were not helpful, or not strong enough to cure what may have caused the swelling. Did you finish the full dose prescribed?
This could just be the flu, or something more serious, so I would advise going back to the doctor as a follow-up blood test may be necessary, and if it's just flu then maybe an antiviral is required.