What should you do if you broke your fast in Ramadan due to menstruation and do not remember whether you made up for it or not, but you predominantly believe that you did?

There is no need for re-qada' (making up the fast), and acting upon one's dominant assumption suffices, for the Prophet, peace and blessings be upon him, said: "If one of you doubts in his prayer, let him ascertain what is correct and complete it based on that." Imam Al-Nawawi clarified that "ascertaining" here means acting upon one's dominant assumption. So, if one's dominant assumption is that the fast has been made up, then there is no need to make it up again. However, if a woman doubts whether she has made up what was due upon her or not, and neither of the two possibilities is dominant in her assumption, then she must make it up. And if she is certain that she owes fasts but doubts whether she has observed them or not, then she must fast them, because the original obligation remains upon her.