Try calming yourself down, the best thing that you can do to help this is to get off of those porn videos, that is probably the reason for all of this. You get so excited and you want to have it so bad that you can't control yourself when a man comes near. Try to ocupy yourself with some other activity that can take your mind off of the sex. Until you get off the porn try to calm yourself down whenever a man is near. Try thinking about something totally irrelevent to sex, and distract yourself away from the the thought of it.