Sometimes going to the doctor can be fun!
When I was in my mid-20s, a situation came up where it became necessary to check my sperm count. To do this, I had to first go without 'intercourse' (but I understood that to really mean orgasm) for four days. Then I had to go into the office and, in private of course, masturbate into a small vial so that they could do the count.
The doctor asked me if I thought I could do that and I said, 'Sure!' However, in reality, I wasn't entirely sure how that was going to work out for me. Between regular sex with my wife and regular masturbation, I hadn't gone without an orgasm for more than a couple of days since I was about 13.
During those four days, my wife and I abstained from sex. I still couldn't resist masturbating but I didn't bring myself all the way to orgasm for fear of invalidating the test. I masturbated a couple of times each day, sometimes bringing myself as close to orgasm as I dared and then letting myself cool off gradually without actually cumming. After four days of this, I was driving myself crazy so I was very glad when the day for the test finally arrived.
The doctor only spoke with me briefly and then left me alone in the examining room. He told me to take my time and to just leave the 'sample' on the table. I could leave as soon as I was finished. The vial they gave me was rather small; the opening was much too small to put my cock into. I wondered just how I was going to manage getting all of my cum in there without spilling it all over the place.
I undid my pants and slid them down to my ankles and started masturbating (I don't wear underwear). I had brought with me a couple of 'men's' magazines to help keep me focused on the subject at hand; doctor's offices are not particularly sexy all by themselves. As before, I brought myself close to orgasm a couple of times to really build up a good head of steam. I also wanted there to be plenty of pre-cum since that is supposed to lubricate things and make it easier for the sperm to come out (apparently that is its purpose). Thankfully, I knew that I was going to finally get the release that I needed so badly so denying myself just a little longer wasn't too difficult.
When I was very ready, I leaned back in the chair and put the vial against the end of my cock so that the mouth of the vial was covering the opening where my cum would squirt out. I stroked my cock steadily and smoothly with no intention of stopping. In just a few seconds, I had a stupendous orgasm... perhaps the strongest of my life up to that time. I felt like screaming with pleasure but I stiffled it and I think I only groaned instead.
When my cock started to unload my cum, it went on for a long time. I could tell, based on how it felt, that I was squirting an exceptional amount. I watched the white fluid jet from my cock in thick gobs and splatter against the sides of the vial again, and again, and again. Each squirt was accompanied by an intense wave of deep, satisfying pleasure that washed over my body and made my head reel. It was hard to keep my eyes focused it felt so good, but the sight of me ejaculating so powerfully and so copiously was exquisitely erotic. I didn't want to miss any of it.
Afterwards, I held up the vial and noticed that I had ejaculated 10 mL of cum. I didn't think much about it, but much later I read some place that the average ejaculation is only about 5 mL. I don't think I typically squirt more than average, but that time I definitely did.
On my way out the door, the receptionist, a pretty young woman about my age, gave me a big smile. I'm not sure if she knew why I was there or not, but I have an idea that she did. I liked the thought that perhaps, she was turned on by the idea of me masturbating in one of the examining rooms. I sometimes fantasied that she went back to retrieve the 'sample', saw my huge load of cum in that vial, and got turned on by it.