I have been orgasming in my sleep for a very long time now- it is just something that I have always done and I have always been comfortable with it. I think the first time it happened was in high school and it happens to me about twice a month. I wake up orgasming and it is, well, nice. It is just something that happens to some people- it is never related to how often I am having sex or masturbating but just the fact that people can get sexually aroused in their sleep. There is a documentary on discovery health that talks about being able to orgasm mentally and without stimulation which is what I think takes place in sleeping orgasms. I have also included a link to an article about that same topic. Hope that helps 
http://www.cbsnews.com/8301-504763_162-20010797-10391704.htmlView Thread
Posted bySuzFleeg(FromGYN Issues: Jane Harrison-Hohner, RN, RNP)