Still no period

I took more pregnancy tests since I am well over a week late. Come up negative. Got blood work. Not pregnant. Is my cycle just changing or what in the world? The doctor did say that my ultrasound results shows a ruptured cyst and maybe that's why i haven't gotten my period but I had that cyst years ago I am sure it just didn't know burst and never had problems with my period because of it. Could I be pregnant and it just has not shown up yet?