Hi,
Welcome to the ehealthforum and I am glad to help you out.
Tubal ligation, regardless of whether the tubes are cut, burned, clipped, banded, or tied, is about 99 percent effective, meaning that about 1 percent of women will conceive an unplanned pregnancy after tubal ligation.
The tubes try to try to heal themselves (like when the ends are cut and sutured,they may rejoin after sutures dissolve), and sometimes a tract(mostly endometriosis) develops that allows egg and sperm to meet.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care.