When I was a teenager, about 15, or so, I used to be horny all the time and usually had to jack off at least a couple of times a day. Hell, every teenage boy did, right?
Anyway, my Mom and Dad got divorced when I was 8, and I lived with my Mom most of the time. My Dad got remarried and lived in another state.
So when I was 15, I was sent to stay with my dad for awhile, He had a big place, and I had my own room that I stayed in. He worked all day, and it was just me and my step-mom at home in the daytime.
One day, I was feeling really horny, and needed to beat off really bad (maybe I hadn't done it yet that day, or something...) and I was in my room, laying on my bed, just stroking away...My dick is pretty big, and I was really getting into it...my eyes were closed and I was just fantisizing about sex shit... After a while, I blew my load and lay there relaxing, holding my dick...When I opened my eyes, I looked over by the door, and my stepmother was standing there holding a laundry basket, kinda drooling with a glazed look in her eyes. I said "Shit!", and she just kinda snapped out of it, and quickly turned around and left.
We have never said a word to each other about that, to this day.