Tubal ligation is considered a permanent form of birth control. It's highly doubtful you could get pregnant 13 years after having your tubes tied.
A more likely culprit in your lack of a period would be the onset of menopause. Before jumping to that conclusion, however, you'd be wise to take a home pregnancy test just to be safe. And then, you'd be well advised to take a trip to the gynecologist to find out what's going on for sure. If you are, in fact, in the beginning stage of menopause (called "perimenopause"), your gynecologist can advise you about what to expect over the next few years.
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