Trung Nguyen,Thanks for the question.On average an individual loses between 50-100 hairs per day, it is greater in patient with AGA. If you only shampoo every 3rd day then it will be much more hair. In young men of your age Male Pattern Baldness or Androgenetic Alopecia(AGA) is the most common etiology. The best approach would be to schedule an evaluation with a hair loss specialist, who can take a complete history, and perform a detailed examination of your scalp to include dermoscopy. The hallmark of AGA is miniaturization of your scalp hair in a pattern distribution. Serious consideration should be given to maximal medical therapy to slow or stop your hair loss and maybe even reverse it!
Bernardino A. Arocha, MD
If you are losing hair with shampooing, then you are probably undergoing genetic hair loss. Your biggest enemy is the progressive thinning leading to a balding pattern that is not evident at this point in time. The degree of thinning that you are experiencing would suggest that you should see a doctor who most likely will get Bulk Measurements of your hair to determine the degree of the thinning that you are presently having. If the diagnosis is early genetic hair loss (the most common cause of hair loss in young men), then the best treatment would be the drug finasteride which is highly effective in men of your age and may not only stop the hair loss but possibly reverse it. If you are developing a more advanced balding pattern the best test to get will determine the Bulk Measurements of your hair and this will show, over a one-year time frame, how effective the treatment will be. Once you know this information, then you and your doctor need to develop a MASTER PLAN which will define what you need to do over the years to come.