Late? Or irregular?

Hi everyone! I used to be on depo. It expired back in May and I never got my second shot. My significant other and I had sex on the days that I was most fertile, not knowing. We didn't use protection. My period is a few days late. The past few months it has been fairly regular. The past two weeks I have had lots of mood swings, cramps, nausea, all the universal symptoms of pregnancy, even though I was only like four days past my fertility window. Also, super important: last night while laying in bed I got a god awful stabbing pain in my left ovary that lasted maybe two minutes then was gone. It was a little painful randomly today but not like the first time. Any ideas? I know the only way to be sure is to take a test. But I just wanted to see some inputs.