I'm at my 2nd week post-op appendectomy. How long would I wait to work out? A doctor said to wait 6 months. Is it strictly a "must" or that long?

Depends. What surgery was done? Open incision or laparoscopic? Surgery complicated with advanced infection? Many surgeons may recommend no heavy exercise for about 6 weeks after a major or open surgery ; likely a shorter time if laparoscopic surgery. Check with your surgeon again to ask them your restrictions for your specific situation.