well don't worry about it..... it happens to many people when they laugh alot(especially girls).... i know many girls that they might be even 20 or even adualt ladies who wet themselves when they laugh alot.... you said that you had to use yhe bathroom too... most of the people who wet themselves while laughing even don't feel they need to go to the bathroom.... the reason that you pee in your pants while laughing was that when you laugh it's like a kind force that decreaces your bladder so you might pee without any control.... so,don't woory and it might happen to you manytimes when you are laughing hardly.....and it;s something completely normal.....