Male,age 62,resting pulse of 39. I've exercised 4 da/wk many yrs and do get lightheaded after workout..OK?

When I was younger and ran more, my pulse was 30 bpm. Over the years, doctors that have treated me and are the athletic type never seem to have any concern about it. Nurses freak out and tell me to see a cardioligist. I'm 5'8" and 205 lbs....do some running, high repetition workouts with weights, and calisthenics.