I'm not sure why your doctor would say exercise won't help you loose weight. And for anyone with pre diabetes or type 2 diabetes a very low carb diet is a must! With an A1c of 6.2 you are having highs somewhere in your day so you need to check your blood glucose more frequently. If the A1c remains higher, even with low carb and exercise, then it may be time to think about meds. Here are some links that might help:
Two great resources for you to ask questions is Gretchen Becker and David Mendosa:
Also check out Dr. Bernstein's book The Diabetes Solution:
David Mendosa has been following Dr. Bernstein for a couple years and it has changed his life!