I have found, read and experienced if one is decompensating/compensating due to a heart problem, the heart rate is almost always above 100 at rest. Cardiac output is stroke volume for one minute. To maintain the same CO to meet the same demand the heart beats faster. My HR was consitently around 115 before going to ER for CHF.
That doesn't mean there cannot be a heart problem with a heart rate under 100 (normal 60-100)
If you have not had an echocardiogram lately, you may want to have one now to check out your heart valves. Heart valves problems have symptoms of shortness of breath, but usually no chest pain. Sometimes a heart attack can have the symptom of shortness of breath, but that would not be constant. Check your blood pressure to make sure that is in the normal range.