If the secretions aren't thin enough, you can cough your way to broken ribs without actually being able to clear any fluids/secretions. (cracked ribs from ineffectual coughing is quite common with pneumonia)
You need to walk down to the pharmacy and speak with the pharmacist. If you were on no meds at all I'd say to go grab a bottle of Robitussin DM. It has both an expectorant (thins secretions allowing them to be coughed up) and a suppressant (reduces the NUMBER of coughs, so that you aren't hacking away exhausting yourself, but when you do cough the expectorant makes them productive ones).
Dextromethorphan HBr 10mg (cough suppressant)
Guafenisen 100mg (expectorant)
HOWEVER, if you've already been given an Rx cough medicine (should have been), you don't want to start overdosing key ingredients. Hence, talk to your pharmacist.
Cough medicine with either alcohol, codeine, or BOTH is the most effective (they make the expectorant and suppressant work better, it's called a "synergistic" reaction, when 1+1=5). Codeine requires an Rx (unless you have friends up in Vancouver or Victoria, and then can schlepp some OTC codeine cough syrup down here for you!), but you have the choice in the pharmacy OTC whether to get an alcohol based cough medicine or alcohol free cough medicine. Always go for the alcohol based cough medicine unless you have a preexisting condition which precludes it.
So sorry you're sick!