I have been experiencing bleeding and spotting for more than one month. what are the reason?

Vaginal bleeding: There are too many possible causes to speculate. The most likely causes vary with age, hormonal contraception, and other factors. If you are under age 25 and sexually active, STDs are high on the list of possibilities -- of course depending on risks (new partner, condoms, etc). In any case, all unexplained vaginal bleeding should be professionally evaluated, so see a doctor soon. Good luck.