Stabbing pain in left pelvic area

Lisa
I've had this stabbing pain in my left pelvic area. It has lasted for ab a month but this past week has been brutal. I have had to stop what I'm doing for it to go away. I'm on the Depo shot and don't have any STDS. I did have to have my left ovary removed in 2009 due to a mass. Any thoughts??? If it continues tonight....I am going to the ER