What Causes Brown Spotting,cramps And Blood In Urine After Intercourse?

I had unprotected sex 15 days ago (two weeks and one day) and today i was having cramps and thought i was on my period; however, later today i saw there was brown stuff everywhere not blood. I looked it up and the symptoms fit with implantation bleeding; brown stuff, minor cramps, but when i use the restroom to go pee some blood comes out like my period but there isnt anything on my under garnments. Is this my period being weird? Or something else?