What's happening atop my head?

[Green]

I'm 22 and I've noticed that my hair is so much thinner and doesn't cover my scalp as it used. Yet, MPB isn't prevalent in my family, at least not at my age. I don't know if this is MPB, normal thinning, stress related...or something else. Any advice would be appreciated as I'm in the dark. My dermatologist did take a look and said "I see absolutely no sign of MPB", however he only looked for about 10 or 15 seconds. Thanks guys.

[Tracy C]

If any of your blood relatives have hair loss, regardless of their age, it is possible for you to have hereditary hair loss. Your age does not matter as much as you might think.

You should seek another dermatologist. One who specializes in treating hair loss. Such a doctor is more able to help you recognize the problem if it exists and treat it to keep it from getting worse - and possibly help resolve it as much as possible.