Anxiety Support Group
Anxiety is a physical condition marked by intense and persistent feelings of distress, fear, angst or dread. General anxiety caused by routine day-to-day stresses usually passes quickly and is experienced by almost everyone at one time or another. However, such feelings that linger over time and are very difficult to cope with, and which lack a clear cause, may indicate...

I agree that it'd be a good idea to go to the ER if needed. Not only may they be able to ease your mind, but perhaps they can provide a treatment that will ease the bronchitis symptoms.
This was what finally cured my bronchitis which has gone on for 4 months: http://www.colloidsforlife.com/silver_Bronchitis.html
I know that everyone mentions going to ER based on the symptoms.
However, my only caution would be to make sure you hydrate your self first and do simple soft breathing to see if any tension relaxes. Doing this first will help you determine what exactly is "off". You know something is not feeling natural, it's just a matter of finding the exact physical symptom, not the anxiety associated symptom.
Best wishes in feeling better!
i agree that what you're feeling is a stretched muscle, and not a clot or anything potentially deadly like that.
i would get back in touch w/ your GP, and let them know the antibiotics aren't working and see if you can get something more powerful. and some muscle relaxers too.