Is It Advisable To Continue Ova Mit During Menstruation?

Hi plz I need help. I have to take ova mit in 3 day in my period.but I never know when I have first day coz first days I dt see enything .b4 4 days I see my period start 3 days left I start ova mit but now it stop and I dt know I have to keap take ova mit or I stop until it start again .plz help me.