Your first reaction to something going badly in a relationship can't be to break up, that's not how healthy relationships work. Communicate. Anyway, if I did that to my boyfriend, he'd find a way to prank me back even worse.
#74 How would that be funny, just imagine the hours of pain where you can't move it and a single movement could make it hurt. Also imagine what happens when you get a boner. not fun man, not fun.
LittleLambii, You're clearly too stupid to understand that somebody gluing their partner's genitalia is not a prank or something that should be taken lightly. This is without a doubt break up worthy at the first offense.
The only prank I can think of is buying a wedding ring box, but instead of a ring, it's a note that says "we're over" and he proceeds to throw her ass to the curb.
There is something seriously messed up if a person thinks that is a funny thing to do. this pretty much destroys any trust you can have in her if she can commit an assault (and yes it is an assault) on you like this whilst you sleep. Seriously you may want to think about where this relationship should go.
Assaulting someone in response to them assaulting you is not the answer, unless it's self defence.
Both the OP's girlfriend's actions and your suggestion are assault.