What kind of doctor would I look up in the phone book for hair loss? Any advice on hair loss? Anything work?

My hair has been falling out for years now and at this point the whole top of my head only has a thin layer of hair. The front of my head still has more but it is fading and I notice it is spreading more and more to the sides of my head. None of my parents have hair loss issues nor did their parents. The thinning out did not start at the top back of my head, so Rogaine is out of the question since it says on the bottle that it is only for the top back of your head; that is if that stuff actually works. In the mean time I have been using shampoo that gives fluff to your hair which helps but soon I will either be bald up top or shave my head and do a military type cut. I'm only in my 30's and this started about 4 years ago, so it seems kind of soon. I almost never wear hats and try not to use gel/hairspray whenever possible. Any advice? Can any kind of doctor give me more info? I am not interested in crazy surgeries or hair plugs. Thanks for any help!What kind of doctor would I look up in the phone book for hair loss? Any advice on hair loss? Anything work?
rogain