What Causes Burning And Itching In Vagina After Intercourse?

hi doctor i am a 24 year old female and Iam married to the man of my dreams. I had Diarrhea a couple of days ago only for one day on that day I had sex with my husband on the next day I had very bad irritation in between the hole in the front and back(at first I thought maybe it was because of hard sex) but it itched andburned when I go to the bathroom,and my husband noticed two small black spots on the side of his pinus the hurt alittle,so my question is can this be serious? and what are the black spots from? I need immediate help