What should I do about the missed fasting days of Ramadan, this past one and those before it, knowing that I am ill and can fast sometimes but feel tired, and how do I pay expiation for the days I did not make up?

"The sick woman must make up the days she missed in the previous Ramadan and earlier Ramadans. Expiation (kaffarah) does not suffice as a substitute for making up the fasts (qada'). If she is capable of fasting, her occasional feeling of fatigue does not permit her to substitute expiation for making up the fasts. If someone owes make-up fasts from Ramadan and the time is too short before the advent of another Ramadan, she should make up the days after Ramadan. If the delay was due to a valid excuse, she only needs to make up the fasts. However, if the delay was without a valid excuse, then in addition to making up the fasts, she must pay expiation by feeding one poor person for each day that was delayed without an excuse. If she was ignorant of the impermissibility of the delay, then no expiation is required of her."