The only way of figuring it out is to either get a program that will effectively hack into you wireless and find the password, or you have to log into your router and check the password on your wireless. If you know your username/password for your router that would be by far the easiest way.
If you don't know it, then you're kinda screwed. The only other option I can think of would be to completely reset your router to default, login with the default settings and set everything back up how you had it and don't forget the username/password or security for your wireless again.
You're not drunk if you can lie on the floor without holding on
(n.): Something that can be looked down on and approved of at the same time.