Hello,
Welcome to ehealthforum and thanks for writing
Woman have reported pregnancy after few years of tubal ligation procedure.Though not common but chances are there.Sometimes scar tissue being left regrows and recanalization of the tube occurs leading to pregnancy.The possibility of ectopic pregnancy is more after this.
If you have any unusual symptom or suspect to be pregnant consider visiting a Gynaecologist for evaluation.A pelvic examination and USG scan would be required and help in precise diagnosis.
Take care!