I agree with what has been presented. I would suggest also going to the ER as they have many more ways of determining what is wrong with you and getting you the right meds.
Yes! Something is severely wrong with you since you've had it this long and it rebound back even after the antibiotics. That's an indicator that what you have may very well be viral in nature. In that case no antibiotics are going to help. Maybe you need IV treatment.
Go to the ER no matter what you look like. Heck! You're SICK for heavens sake.