I've had persistent flu like symptoms, have seen the doctor 3 times in 3 months, and it seems to be getting worse. Antibiotics are not working. Why?

Hmmmm... If you mean runny stuffy nose, sore throat fever and fatigue, for that duration, I'm thinking mononucleosis. Antibiotics wont help mono. Supportive care and time is the management for mono.
See another doctor. This may not be something that antibiotics is going to treat. Persistent flu like symptoms is a little concerning. If your symptoms are headache/fever/chills/muscle aches/sore throat, etc... There is something serious going on. I would see someone who is going to do more than treat with antibiotics.

Related Questions

I've had flu like symptoms for 2 weeks now. The doctor has given me antibiotics for a sinus infection but I'm still feeling achy, breathless, hot and cold and no energy?

Time for recheck. Most uncomplicated viral illnesses get better within 5-10 days, even if treated with an antibiotic for a bacterial infection. The fact that you're going 14 days without improvement in symptoms is concerning. You should absolutely followup with your doctor- they'll re-examine you and see if this is the normal course for your illnesses, or if there's something else going on.