I have a rash on my butt, it goes from the bottom of my butt cheek, in the crack, & to about the middle of my butt cheek. It came up about 30 minutes after my boyfriend & I had sex, "doggy style", if you may. It's like mosquitoe bites, it itches but after I scratch it it becomes really sore. Is this something to worry about or could it be a contact rash?