Infection. I have an antibiotic and a kuhrrraazzee cough syrup.
If they gave you antibiotics, they think there's at least a chance you have a bacterial infection. I'm no medico, but personally I would lay off, if possible, for a few days until the antibiotic has a chance to kick in. Also, I would thoroughly wash mouthpieces, and get rid of reeds I was using immediately before diagnosis. You don't want to reinfect yourself! (I always throw away toothbrushes at such times too, for the same reason.) Hope you get better soon!
If I had a paid gig and didn't have a fever over 99.9, I'd likely play the gig and then clean the horn; this is not ideal, but after all there are other people depending on you (hey, you can infect them too!). Actually I have had a couple of very satisfying experience playing gigs when I had a fever. . . . But I'd leave off woodshedding; you can do some mental practicing and/or serious listening while you're off your feed.
Years and years ago I went off on a 3-day road gig when I had what turned out to be mononucleosis! Big mistake. You've been diagnosed, so you're fine, but I would never again go to a gig ill not knowing what the problem was. You never know.