I recently started an exercise routine to lose weight and i had one abnormal period (heavy bleeding) and now a missed period. should i be concerned?

Observation: Stress, weight loss, medication, exercise, menopause and other benign things can cause menstrual irregularity. If your cycle does not resume a normal patterns in a few months, a visit to your gynecologist is suggested.

Depends...: Very strenuous exercise can affect your periods, and can even stop them altogether. Seen sometimes in female marathon runners, for example. That being said, check with your gynecologist - might want to get some blood hormone levels.