N3000 I can't help feeling that your doctor is fobbing you off, treating a symptom rather than the cause. I've had similar symptoms from about your age - my doc's suggestion: 'workaholism and stress, take a break'. Takes a bit of getting used to needing less sleep as we get older too. I gave up going to bed early, just ended up having a short deep sleep then lying awake for hours. Try some new enthusiasms/activities, cultivate a personal 'hinterland' outside work - something physical maybe.
Best of luck!