the "bloodletting" which takes place during menses is a means of detoxifying. the cleaner a person is, the less they will bleed from any breach. most women athletes find that once they have their body fat percentage down to a certain level, their period stops. for most women today, the period becomes heavier and heavier as the body learns and relies more heavily on this avenue of cleansing, their body becoming more toxic from diet and lifestyle. fasting and proper diet is the cure(the cure for all things). you are pulling toxins out with the oil pulling and this has decreased the need for sloughing so much blood.
it is a good sign that your body is still responsive and effecient. most women have noticed some kind of difference with their period after starting to pull. except for alrm from fear of the unknown, those changes are almost all positive.