Based on what you have described, it would be unlikely for this to be a heart issue. While you do smoke, have high cholesterol and have family history of heart disease, you are still only 25 years old. Symptoms like you describe -- two straight days of pressure on back, shortness of breath, cough, cold sweats, etc, would point more to lung disease such as asthma attack or even pneumonia. Occasionally using rescue inhalors could actually make people sweaty and gittery -- could this be a trigger for your symptoms? I was unfamiliar with Primatene Mist -- but it appears to be epinephrine so it certainly could drive up people pulse and cause palpitation.
Therefore, I would recommend stopping smoking immediately, stop the inhalors if possible. IF symptoms do not improve, consider getting a CT scan of your chest, lung and heart (a coronary CT angiogram would serve this purpose). This would rule out a lung condition, and firmly rule out any coronary abnormalities.