Since this is only happening a few times a month, and started at about age 13, are you positive you're not having wet dreams instead of bed wetting? Wet dreams start with guys between about 10-13 and are often mistaken for bed wetting. The difference is that there's far less fluid in a wet dream and the fluid is thicker than pee. They can be just as embarassing sometimes, but it's a totally different reason behind them. They're nature's way of telling you that you're a man now. Other great medical Web sites like http://www.puberty101.com/p_wetdreams.shtml can help with more questions like this. As I told someone else... if bed wetting has started after years of not happening, something has changed... see a doctor as soon as possible to find out for sure what's going on.