What is happening to me? Is happening?

Here's my story: My first day of my last period was on April 9, the period went on for at least 6 days. Im pretty sure that my ovulation date was April 23 or around that time. I had unprotected sex during that April 23 for 3 times. We're not trying to conceive. After that in April 30 I noticed a little amount of brownish discharge, same goes durinh May 1. May 2 to 6 was different, I bled heavily that I can full a napkin or a pantyliner. The blood was thin and color bright red and sometimes dark/black and dont smell like a period. The heavy bleeding has no clots too. It stopped on May 6. My expected period was May 9. Before my expected period i experienced little vaginal discharge. And now that I am 3 days late (May 12) i am experiencing lot of watery vaginal discharge. I have upper and lower back pain, and abdominal pain when stretching My body. But nothing else like PMS or Pregnancy symptoms right now. I dont want to get pregnant as of now. What is happening? Thank you for your help!