What Causes Light Period Bleeding?

I am taking femilon for last 2 years. Since last 6 months I find my menstrual bleeding is too reduced- It is just a spot like. Now i can t understand whether it is going on or not. I consulted one gyneacologist who stated that this is normal and good for health. is it so? Pl. suggest shall i continue with it? I have no other serious health problems.