This experience is from more the 10 years ago, when i was 20, and probably one of the events that trigger after years my PE fetish.

In that period i had a light crush for a girl i will call Liza, between us there was a good alchemy, but she was in a continuous back and forward with her long term boyfriend.

I had free home and organize the a party with some common friends. Liza ask me to bring also her friend Kate, I know also her, but we never talked too much.

The party was nothing big, like 15 people all around twenty, lots of alcohol, and some bad music,
After some drink, i take the courage to flirt quite directly to Liza, she take me a part, a tell me straight forward that due the situation with her bf, she don't want any relation, she also tell me that Kate was really into me, and that she see us good together,
With Kate i had just some brief chat before that night, i considered her out of my league, she was a short girl with a nerdy look, huge tits a rounded ass, she also had more sexual experience respect me.

In any cases, the confidence given by the words of Liza and most from the alcohol, made me engage Kate, we start to talk, drink together, flirt, until we search some privacy in the garden.
We start to kissing, than making out and touch each other, i was already fully hard, i put my hand below her shirt and start to touch that huge tits (they still the bigger tits i have ever touched), while Kate hand was laying on my cock over my pants.
That boobs drive mi crazy, after like 30 seconds of making out while touching her boobs i completely loose control, and jizz myself, her hand still was on my cock, she remove it when the wet spot start to appear on my pants.
I was petrified, she look and me a say something like "Oh that was unexpected... Don't worry i take it as a compliment, but now it's better if you go to change your pants"

I disappear in my room for few minutes, to clean and change my pants. When i come back to the living i was still quite embarrassed, but i trying yo not thinking to much, the party was still on going, but some friends started to leaves so i get busy with the greeting and so. But i see Kate giggling with Liza both with sly face.
I had tried to talk again with Kate, but there was always someone around.

Some time later, it's time also for Liza and Kate to leave, I accompany them to the garden gate, both hug me for the greeting and thanks me for the party.
They just turned the corner of the garden, behind the hedge, when i heard Kate say something like "I hope his not jizzed himself for our hugs", both girls start to laugh loudly. I'm quite sure they didn't known that i was still in range to hear them.

Despite this, in the following days i wrote to Kate, ignoring what happen, and asked her to go out. She simply answered that during the party she get really too much drunk and lose control, and that she wasn't ready for a relation in that period, but she really enjoined the time together and we can remain friends.

At that time i was into this kind of fetish, so I felt really embarrassed and humiliated, even if thinking to that moment (making out with Kate), made me always hard, i also masturbate to that several time.
I really don't know how fetish development works, but if i need to bet, i would say that this experience is related to my fetish.