What Causes Sharp And Continuous Pain In Lower Pelvic Area?

Hi! I'm a 29 yr old female. For the past 3 days, I've been having a really sharp, continuous pain in my lower left pelvic area. The pain gets worse when pressure is applied to it or during sexual intercourse. My 25-29 day cycle has been irregular and I am not on birth control, but i had a period last week which only lasted 2 days (usually lasts 4-5 days). What could this pain be?