Face it, they're going to find out! Either the smell will give it away or they'll notice you washing all your blankets & sheets every day. Better you show you're responsible and tell them yourself. Then you'll have more say in how to deal with it. If you wait for them to find out they'll think they have to make your decisions for you (like what you wear to bed). I tried to hide it from my parents and didn't find out that they knew until one night at bedtime, with my mom telling me to take off my pants and lay down!