Has this happened to anyone else? Paragard?TMI

Okay my iud fell out unknowingly around the 7th. Which is around my fertile window. I dtd around that time not knowing. My AF was supposed to come on the 22 which is did. Instead of it being 5 days it was only two, bright for about 2 hours than really light to non existent for the rest. Fast forward to today, I am sitting on the couch and I sneeze, and a big gush of blood came out, bright red. I am now having slight cramping on my left side, but no more blood. I called the ER and they said come in if I start bleeding heavy, in the mean take a HPT and follow up with my doctor in 2 weeks. I am so confused though. Has anyone else ever experienced this? What was the problem?