I had started having wet dreams when I was 12, but didn't know what they were (we didn't have any sex ed in school back in those days -- at least not for 6th and 7th graders. I had a friend with whom I played around a little bit -- we showed each other our boners (I was much further into puberty, and loved the V that he still down to his immature cock). We even rubbed our cocks against each other's assholes once, but didn't know you could do anything more than that).
One night when I was 13, he stayed over night during Christmas vacation. When we went to bed in my room (I had twin beds for just such an occasion), he said he wanted to "fuck." Though I had heard the word, I didn't even know what it meant. He had me put my rigid cock through the slit in his pajamas and I rubbed up and down between his thighs -- it felt good, and then it started to feel REALLY good -- and then I had my first waking orgasm. Again, we had no idea what it was. He complained that I had peed on him, and in the morning because his pjs were all crusty!
I had no idea how to repeat the feeling, but a month or so later, I was in bed at night, and my penis was wrapped in the folds of my pajamas and rubbing up and down felt good again -- and I came again - now I knew that it was repeatable. The next night, when I got home from school, I went to my bedroom and put my pjs on immediately, and tried to repeat the procedure. My mother called to say dinner would be ready in five minutes -- I pulled out my cock and started rubbing it instinctively, with my hand -- and I came. After that it was at least every night, and sometimes more often -- always on my sheets -- and I knew it left a stain, but my mother never said anything. We didn't talk about things like that at all!
Still enjoy rubbing one out, though now I use a cock ring and lube.