I have had 4 previous mi's. At night exper. Chest heaviness but no pain? Some wheezing. Minor discomfort taking deep breaths. Is this another mi?

Unable to say. Heart attacks can cause many different symptoms. In any given person it is impossible to diagnose a problem without a true evaluation. Because of your history you should be under the care of a physician with experience in cardiovascular disease and should call with any new or unusual symptoms.
Diabetes?Smoking? In patients with diabetes, chest heaviness may be your unstable anginal equivalent or even sometimes that is all you may feel while having a heart attack. This is obviously a serious matter and i think you should insist to your cardiologist that your symptoms are serious enough and want a coronary angiogram. Coronary stents do close specially in diabetics. If you have coronary stents, r/orestenosis.