If your periods have been like clockwork and this is one exception, there may be some hormonal imbalance this month that is an
isolatedIsolated sleep paralysis event. Given that, it might make sense to wait one month and see if it happens again.
One thing to consider is that even though your tubes have been tied, it is still possible to get pregnant - unlikely but possible. You could get a pregnancy test over the counter and just be sure that isn't the case. If the pregnancy test is positive, or if this happens again, I would suggest making an appointment to see your doctor. He/she might want to do an ultrasound and an exam and perhaps run some hormone tests to understand what is causing the problem.
Machelle M. Seibel, MD