So after i come, Why is the tip of my dick so damn sensitive..It's to the point where if the girl grabs me by the head of my dick

it's an instant reaction to pull away from her..I can't help it.
Put it this way, If it gets touched, Sucked on or whatever within a few minutes after i have came..It makes me buckle with pleasure.
What causes that? I'm sure i'm not the only guy.