I am 5 days late on my period and have really stabbing pain in left ovary. Had a tubal ligation 4.5 years ago so don't think I'm pregnant what could this be?

Still possible. Tubal ligations aren't 100% perfect, tuba pregnancies are still possible. This is unlikely however; an ovarian cyst would make more sense. If the pain persists, don't wait he must see a physician.