Advice for possible hair loss prevention..

I'm a 22 year old male.  I'm occasional drinker and smoker, typical college student.  My Dad is bald and but both of my Grandfathers are not.  I've noticed a slight pain when I run my fingers through my hair and notice that my hair is falling out when I do this.  Now, I'm not saying I'm going bald or anything, my hairline has been the same my entire life.  I'm just wondering if there's any supplements out there or programs that prevent hair loss just in case it might be happening?  Thank you...