What are the consequences of not making up the days of missed fasting due to menstruation in Ramadan?

What you used to do by breaking your fast during menstruation is correct, because it is not permissible for a menstruating woman to pray or fast, by scholarly consensus. However, your failure to make up the fasts is undoubtedly a mistake. A menstruating woman must make up the days she missed, by scholarly consensus, due to Aisha's saying: "We used to menstruate during the time of the Messenger of Allah, may Allah bless him and grant him peace, and we were commanded to make up the fasts, but not commanded to make up the prayers." You must calculate the days you failed to make up and hasten to make them up. For every day you delayed making up until after the next Ramadan, you owe the expiation of feeding a poor person, according to the majority of scholars. However, if you were unaware of the prohibition of delaying, then there is no expiation upon you. If you are unable to calculate the days, then you must estimate and make up what will give you certainty or a strong presumption that your obligation has been fulfilled.