I am a 20-year-old girl. I reached puberty when I was 13. I started wearing the hijab when I was 15. I used to not fast in Ramadan regularly back then. About two years later (as far as I remember), I started to be a committed Muslim. However, I did not observe the days of fasting that I missed in Ramadan back in those days. I started to make up for those days about three years ago, but I have not finished yet.
I have been lazy regarding finishing those days. I knew for sure that I had to make up for those days. However, I did not do so, maybe because I needed somebody to talk to me about this obligation and draw my attention to it. I do not know. Thanks to Allah, I pray, recite the Quran, and commit myself to acts of worship. I am burning inside out of regret because I know that I am still required to make up for too many days. I almost forget exactly how many days I missed or when I missed those days. I would love to observe regular fasts on Mondays and Thursdays. However, I learned that I would not be able to offer voluntary fasts until I finish the days that I have missed in Ramadan. What can I do? I did my best to make up for the missed fasts, but what else can I do? I told my mother that I need to pay an expiation, but she replied that she and my father have been doing this for years already. Is that right? Could you please advise me?

All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

You are required to make up for all the days of fasting that you have missed in Ramadan. If you are not certain about the exact number of days that you have missed, then do a serious calculation and fast a number of days regarding which you will be certain that you will be cleared of this obligation. The obligation of making up for those days never ends, no matter how long you have missed those days or how uncertain you are of their exact number. Also, you are required to observe the expiation that is prescribed for the inexcusable delay of making up for those days until following occurrences of Ramadan come over. If your mother pays the expiation for you without your permission, then this is not permissible. This is because you or whoever you authorize must make the intention for paying the expiation.

Allah knows best.