Hi bin_man...........
Are you currently on any medications that might have side affects that might be causing the hair loss.. you could have a thyroid problem.....it could be the shampoo, which might be drying....in any case you need to get yourself to a doctor to see what is going on.... In the mean time If you scalp is dry and itchy you might try an olive oil treatment for your scalp...
hope you find some good answers to your question on the boards..................jennie, az