That is a low dose of Metoprolol, and I do not see where you are on an
ACE inhibitor, which I believe are part of the MI guidelines. The beta blocker of course can make you tire easily. A 14-16 hour work day sounds a bit much to me........no wonder it takes 2 or 3 days to recover! Maybe you can try to cut back some? Your heart rate isn't that high, but higher than I would expect. I am not a doctor, though, but I would see about getting the beta blocker increased and add an ACEI.