I understand your worry about your late menses. According to your medical history you had tubal ligation 18 years ago; I agree that no contraceptive method is 100% effective and there are documented successful pregnancies even with this procedure but certainly the chances for you to be pregnant at the moment are minimal.
On the other hand, there are other possibilities for your late menses and even missed periods could happen from time to time, all these been totally normal.
If you want to take a pregnancy test, the ideal day would be a week after your expected day of menses, if menses are still not present in your next 2 to 3 cycles, a visit to the gynecologist would be recommended to rule out hormonal imbalances such as early menopause. I wish you the best.
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