Losing of Hair

I always have had good hair on my head, thick and rough, and used to use lots of hair gels, and creams pretty much daily. But over the last 2 years i have started to lose my hair. I have visited many doctors to search for treatments, but they all give different advise and mention that using shampoos and some lotions will fix the problem. But unfortunately it hasn't till date.
I faced the same issue 6 or 7 years ago when suddenly i lost a lot of hair but after some treatment, it went away.
I have been using medicated shampoo for nearly 2 years now and eating some prescribed by none of this helps. I would like to mention that I have massive dandruff problems which has been there through out my life and also have itchy scalp, especially after shampooing.