Here is some additional information for you.
Doctors call the absence of menstruation -- amenorrhea.
If a woman has never had a period, it is referred to as -- primary amenorrhea.
In cases like yours, where menstrual periods have ceased -- they call it secondary amenorrhea -- click on the link for a thorough explanation of this disorder.
Although you now have access to comprehensive information about your
condition -- having this information will neither pinpoint the exact
cause of your problem -- nor will it change anything.
I have given you all the help that it is possible to give you
here. Your condition is likely to change only through
examination, diagnosis, and treatment by a physician.
Let me know if you need more input. If not, thanks for the
opportunity to assist you... I would really appreciate your honoring my
efforts by 'pushing the button' and Accepting this answer. Adding
a bonus -- should you wish to do so -- is always warmly welcomed.