Hello, I have gone through your query and understood the concern. If you have always had regular menstrual cycles without any disturbance, are sexually active without any contraception, this irregularity must be investigated. An estimation of the serum beta-hCG titres followed by a trans-vaginal sonogram help to exclude/confirm pregnancy and also to know the status of the pelvic organs. If negative, hormonal imbalance should be suspected and attended to. Sudden weight disturbances, stress, infections and certain medications can alter the menstrual cycle. Local causes for the intermittent spotting include erosions, infections and polyps. Hope you find this information useful. Take care.