Advise On Itchy Vagina And Clumpy Discharge After Unprotected Sex

I am 21, 5'5", 140lbs. I had unprotected sex and now, 3-4 days later my vagina is itchy. He doesn't have any visible or symptomatic STDs and I haven't slept with anyone in a LONG time. I'm supposed to get my period this Thursday (today is Sunday) and I'm having this discharge that kind of looks like clumpy poo. Like soft stool. It's not that gooey maroon blood clot discharge. It honestly looks like skid marks. And my vagina and kind of my butthole are itchy (no I did not have anal sex). What's going on?