How can the questioner make up for the days she missed in Ramadan 2001, and the days she is unsure about not having made up from Ramadans between 2002 and 2015?

One must repent to Allah for intentionally breaking the fast in Ramadan (definition), count the number of days intentionally missed and for which the make-up was delayed but not performed, and hasten to make up all of them. If the exact number is unknown, then one should strive to estimate and act upon the predominant belief, making up what one believes, with a high degree of certainty, will clear one's conscience. If one is certain that a make-up is due but doubts whether it has been performed, the default assumption is that it has not been performed.

According to the majority of scholars, in addition to making up the fasts, one must feed a poor person for each day whose make-up was delayed without a valid excuse, unless the questioner was unaware of the impermissibility of delaying the make-up, in which case the expiation is not obligatory upon her.