Severe cough early oct, then bad bronchitis & now increasing cough w/ severe, radiating pain under left breast w/each cough. could my rib be broken?

Yes Could be Broken: There are a number of other possibilities, as well. Needs evaluation. Expect to have a Chest X-Ray, possibly a CT of the Chest. Further studies might include a bronchoscopy for a direct look inside your lungs possibly to have a sample of tissue removed for diagnosis. There are other minimally invasive procedures that might also help come up with an explanation of what your problem is.