Even into my 50's I still have pretty vivid wet dreams maybe once or twice a month and like the OP I usually wake up as I'm cumming in the dream and continue to cum for real till I'm done  :fap:. I find it happens more often if I've been thinking about sex as I fall asleep. As a teenager I used to have them once or twice a week or more and I used to think there was something wrong with me too  :crazy2: