my throat hurts BAD when I breathe hard (and other causes)

A typical day for me:
I did a workout today in PE. 10 160 m direction changing sprints. The first three I was under 30 seconds. After that I decided that I didn’t want to damage my throat, so I slowed down to 40 seconds. My throat had a burning pain that kept getting worse. It felt like it was being dragged across some dry, rough surface. Less severe pain also radiated through my chest. After I finished I drank some water. It helped a little, but not much. After a day my throat still felt dry and I coughed a little. There was a lot of mucus that I have to swallow.

I have been living with this for a long time.
There is almost always extra mucus and sometimes pain in my throat.
Whenever I am sick, my throat is the epicenter.

Things that aggravate my throat:
*Breathing (moderate or hard)
Water in my throat
Smoke and dust
*Yelling and singing
Talking
Food
- *Citric acid
- Sour food
*especially this

What is causing this and how could I treat it? My doctor put me on antibiotics and that didn't help.
I have seen an ENT and he thought it could be some kind of acid reflux, but Nexium didn't help.