It was in 1970 when my girlfriend's sister was driving my car and my girlfriend and I were in the back seat with a blanket over us. She undid my pants and I undid her bra.
While I was fondling her boobs, she was jacking me off. After I shot a load, she did not stop stroking my dick. She continued fondling it until it got erect again and then she jacked me off again and after I came again, she continued to beat my pork for the third and last time.
I don't think her sister knew what was happening in the back seat unless my girlfriend told her after I went home. Any way, when I saw my pecker when I got home, the damn head of my cock was swollen up like a partially blown up balloon. I called her the next day and told her and she started crying. I told her to stop crying and that the head will return to normal. (At least I hope it was going to.) It did, thank goodness.