Just felt the worst pain of my life!!

We were just doing regular doggie, and suddenly I felt the absolute worst pain of my ENTIRE life. I can type now, because the worst of the pain is over, but it felt like this MASSIVE gas bubble trapped inside of me. Like I'm going to have the most painful poop of my life.. I was just literally screaming for 20 minutes. A hot shower eased the pain a bit. All the pain was in my lower stomach and lower back. Has anyone experienced this before? Appendix burst? Bowel blockage? Ectopic pregnancy? I keep getting these random light lines on pregnancy tests for the last couple of months.. Thank god, the pain has let up..my SO had to go back to work, but I am just wondering if anyone has experienced this during sex?