Spotting After +OPK with Cramps mid cycle TMI PIC

Bethany
I took my Nuva Ring out 7 days ago, mid cycle and got a +opk yesterday and my CM with stretchy. So we had sex. And now today, I am cramping slightly and having spotting. With a tiny clot.  hy?  What could this be? 
I'm
Confused because I got a positive opk and I took my BC out a week ago.