It sounds like you are just beginning to manifest the changes of male puberty. It's a tough period for a young man like yourself, but hopefully your parents or some other respected elders can help answer your questions and guide you through it. Wet dreams are actually pleasant dream experiences that happen when you are asleep. Your dreams may be sexual in nature and during these dreams, your penis may become erect and spontaneously ejaculate or emit seminal fluid. This fluid is milky and white and often a bit sticky and slippery at the same time. This is a perfectly normal occurrence and it happens to adult men all the time and there is absolutely nothing at all to worry about. Get yourself a good book on male puberty and do be sure to read up on it. I hope this answer helped you with this concern!