Mid cycle bleeding now late period

Hey everyone! This is my first post on here, and I have to say I'm a little flustered!

Two weeks ago, my partner and I were having sex, and in the middle of it I started bleeding. I didn't think it was my period because that would have made my period two weeks early. I did continue to bleed for four days, red not brown, but like two of those days I barely bled at all?

Fast forward to today, I am two days late and getting negative pregnancy tests. What is going on with my body?? Has anyone experienced this before??