Your cycle can be late for reasons other then pregnancy. It could be something like an ovarian cyst or hormone levels being a little off. Even stress has been known to affect your cycle. If you don’t get a period you can try doing another home pregnancy test (since tubal ligation aren’t 100%) or call your OB/GYN to see about going in for a pelvic ultrasound and/or some labs. Wishing you the best!