What Causes Burning Feeling In Throat, Coughing Fits, Dry Cough And Lethargy?

Question: Thursday, a week ago I had a burning feeling in my throat, then had days of feeling quite lethargic that weekend, then developed coughing fits due to a dry cough, so did inhalations and took Rikodeine, but then that did nothing and I started coughing up deep yellow phlegm. I noticed that the tickle only subsides when I cough deeper and get rid of the phlegm.

I went to my GP on Thursday this week. She said as I had no sinus congestion or fever that it was viral and antibiotics would not help and I could expect to keep coughing for a couple of weeks. She gave me an Amoxil antibiotic as I am a singer and have some concerts coming up, but said it probably wouldn't do anything. She was right and now I mostly cough deeper automatically and cough up yellow phlegm.

The reason I am writing is to ask whether I should be on a different antibiotics to clear the phlegm and I have noticed occasionally when sleeping on my side whether left or right, after having cleared some phlegm after a deep cough, I felt and heard a rumble which started from my stomach or bottom of the lungs and rumbled all the way up the middle of my chest and out the top of my throat. I was trying to work out if it is connected to inhaling or exhaling but it still happened even if I held my breath.

I tried again now to see if it would happen again, but nothing. I think it may have been trapped air from the coughing action? Do I need a different antibiotic to clear the phlegm, or just wait for it to get better? The colour seems to be getting lighter day by day. Should I continue to take Amoxil or stop?