What is the ruling on making up for many years of fasting due to menstruation or postpartum bleeding, considering that the questioner is 21 years old?

If a woman has not made up for the Ramadan fasts she missed due to menstruation or postpartum bleeding until the next Ramadan begins, and if the delay was without a valid excuse, then she has disobeyed Allah and must repent. She is obligated to make up the missed days along with an expiation for the delay, which is a mudd of food (approximately 750 grams) for each day. However, if the delay was due to a valid excuse, such as an illness from which recovery is hoped, then she only needs to make up the fasts without expiation. If the illness is chronic and recovery is not hoped for, then the obligation is only to feed the poor.