I Take Metoprolol Tartrate. 2 Tabs / Day - 25mg

I take Metoprolol Tartrate. 2 tabs / day - 25mg (50 mg/day total). I believe that may be high. My last BP check was 110/67 at the dentist's office. Friends have told me that my dose is too high! I have been on MT for about 10 years and am 67 years old. I don't seem to have any walking or running stamina and have had two stress tests because of shortness of breath. They came out - NO problem. My meds were not changed. What is the right answer?