18 and loosing hair FAST!!!

[Krissundersea]

I am 18 Years old. Turning 19 in December 2009. About 5 Months ago I had really nice hair. I never kept it long, just short and had a hair cut at the barber shop every month.
       About 4 Months ago is when i noticed my hair is getting very thin on top and on the vertex. I bought a Shampoo and Cell Therapy Called Ovation. Didn't work. So i then talked to my doctor and he proscribed me Propecia. I was very Excited thinking it would work. Well i have been taking it for 1 Month and well haven't noticed any results. I know they say to wait at least 9 Months, but i am still shedding hair. When i shower and every time i comb my hair with my hand im loosing about 20 Hairs. So I cut to taking showers every-other day. And when i wake up and look at the pillow, there is about 15-25 Hairs on my pillow every morning. I am very scared. My dad does is bald. and my grandpa ( on my moms side) I guess Baldness is normal in my Fam. But really at 18????? Should this be happening. Also every Hair that falls out has a white tip. Maybe this is the follicle or the root. Can hair still grow back in that area where the hair fell out with the white end.? Please help. And when should i notice some results with Propecia.?