Ask the doctors: How can I tell if I’m sleeping enough?

I have always had difficulty sleeping. Since I have taken to heart the advice for good sleep habits, I think I?m sleeping better, but I?m not sure. I?m in bed about 8.5 hours, but am often restless and get up to go to the bathroom a couple of times during the night. Is there a way to compute how much sleep I?m actually getting?