Whenever i start exercising again, i start spotting. am on bc for anemia. had breakthrough bleeding and some cramping for over a month when i started an exercise-heavy job, even on bc. what does exercise affect that causes this? do i need stronger bc

Low estrogen?: If you are slim and in excellent physical condition, you may be low on estrogen. If so, a higher dose oral contraceptive might be a consideration. Otherwise, this definitely needs further evaluation; any and all abnormal or unexplained vaginal bleeding needs professional care. Don't expect conclusive answers on a forum like this. Contact the doctor where this problem has been managed up til now.