My doc gets on me every year about workingout but he looks worse than I do at same age. Is he credible?

Perhaps, but.... My father-in-law, a gp for 50 years, was in reasonably good shape, but never exercised. When his patients asked him @ exercise, he would half-jokingly say, "when you think about it, sit down till the urge passes". Sadly he died of heart disease. Doc's credibility relates to whether it results in ur exercising. Either way, he's correct: exercise 30 min/4 days weekly. Will likely outlive ur doc.
? Why are you worried about your doctor and following his own recommendations? You should be worried about yourself. If he recommends exercise, then you choose for yourself whether you will listen to the advice or not. Saying I'm not doing it because my doctor doesn't do it won't help you when you're dead before your time. If you want a 2nd opinion, then go ahead and get it. It's your body & life.