The first time I came, strangely enough, was not the first time I masturbated.
The first time I came was when I started my secondary school aged 11. Big grown-up gym with tons of new equipment, including climbing ropes. By the age of 11 I'd climbed hundreds of ropes but not like the ones you find in a gym; thick enough to grip between your feet and thighs. I jumped up and grabbed it and worked my way up it. With each grip/push stroke I started to get this incredible feeling in my groin which got stronger and stronger with each stroke, until just before I got to the top this fabulous feeling overwhelmed me and it was all I could do not to let go and fall. (great! - schoolboy dies in gym accident: suspicious stain found on his shorts!) Given that I can imagine the rictus expression on my face, I'm suprised the gym master didn't notice. The same thing happened the following week, and the week after, and then - horror - nothing! I was bitterly disappointed. It took me another week to work out that I could generate that fabulous feeling all by myself - and without the aid of a rope! Seldom missed more than a couple of days since then.
The cum turned up a couple of months later. One odd thing, though, about a month after that, my best friend and I were having a mutual jackoff session and I trying to see who could cum first (him, as usual) and after I'd finished I noticed I'd shot blood rather than cum. I was frightened, of course, but more embarrassed really and quickly covered up and went home (aren't kids dumb, eh ?). I worried about it the rest of the day, then went to bed and tried again and had yet another mind-blowing orgasm and - great relief - a nice blob of ordinary cum. phew!