Thanks for posting on HCM,
It would have been best if you redo another pregnancy
test just be sure, then at the same time see a gynobs for proper evaluation. You will need a pelvic ultrasound
too. There are other pelvic diseases that can mic mic a state of pregnancy and those have to be ruled out as well. Tubal ligation
is not a guarantee for permanent sterility
and you still run the chances of getting pregnant if the tubes spontaneously untie.
It is best you see a doctor as soon as possible.
Hope this helps