Why does my dog pee everywhere when we have sex?

every time me and my wife do the deed, my dog sits outside the door and paws at it and barks. we can hear him running around. when we come out there is always piss everywhere. we dont really punish him for it because he always acts scared. does anyone else have this problem?
Update: he's a 10 month old Boxer
Update 2: i didnt mean to make it sound like i have sex with my dog
12 answers 12