Could you be psyching yourself out about the antibiotics? I have actually thought I was having terrible allergic reactions after taking things like aspirin, when in reality it was just really bad anxiety because I didn't want to be taking whatever medicine. I've never heard about achy knees being a sign of a reaction? Maybe call the nurse hotline just to be sure?
For what it's worth or for future reference, I have cured strep throat and other awful similar infections by just drinking 3-10 packets of emergen-c a day. It takes longer, but it always works. I have a bad immune system and get terrible illnesses/infections all the time. But I haven't taken a antibiotic in years. I've been written dozens of prescriptions for them though...
I personally, don't take probiotics while taking antibiotics. Mixing them up just weirds me out. Then after treatment I just go extra heavy on the probiotics. I've seen many threads here on MDC address this though and they've said to wait a few hours after each dose, and then take the probiotics.
Sorry no one's replied.

No one every replies to my stuff in this forum either.