I think you have folliculitis, or blocked pores, perhaps from the sweat and friction of sex. Rather than drive yourself a little crazy with worry, why not see a doctor as soon as you can (walk-in, STD clinic) and get a proper diagnosis. If I'm right, then you really don't even have to treat it, because it will go away.
And avoid unsafe sex--the risk and anxiety aren't worth it.
Take care.
Dr. Rockoff