Aside from a stuffy nose and some general muscle aches, a cold or the flu shouldn't make you short of breath or cause pain in your chest. These could be signs of a more serious problem such as heart disease, asthma, or pneumonia. Call your doctor or go to the emergency room.
If you're one of those people who brag, come flu season, that you "never, ever get sick," be aware: The odds may catch up to you. Every year, about 5% to 20% of U.S. residents get influenza, according to estimates from the CDC.
Taking certain antiviral drugs within 48 hours of the onset of symptoms can shorten the duration of the flu, but that involves recognizing you have the flu, getting in touch with your doctor, and going to the pharmacist before the 48 hours is up.
Just in case your number...
A cough that won't go away is likely postnasal drip that can be treated with antihistamines. But it could also be related to asthma or GERD (gastroesophageal reflux disease). Your doctor can tell you about treatments that can help.
A lasting, severe cough is also the main symptom of whooping cough, which has become more common in many parts of the U.S. So, if you have an unexplained cough for more than 2-3 weeks, your doctor may test you for this type of infection.