Could be a pelvic floor muscle spasm or maybe it has to do with the prostate... like prostatitis, an inflammation of the prostate. It could also be that you're really nervous about it, which constricts things and prevents you from relaxing your smooth, urethral muscles to ejaculate. Physically, your body has to hold back any urine in order for you to ejaculate because you cannot urinate and ejaculate at the same time.
First thing to do is to discontinue riding that darn scooter!
Now, you could have experienced retrograde ejaculation, which is what happens when sperm enters the bladder. I dunno the reason... maybe because you're nervous about the testicular discomfort or nervous about not ejaculating as much - our minds can really mess with our nerves - or maybe you're taking some weird medication that's giving you that as a side effect. Retrograde ejaculation is not life-threatening and shouldn't cause any pain, but it would freak you out to have less ejaculate, a dry orgasm, or a less pleasurable orgasm. The worst effect of this would be infertility. Personally, I would try some pelvic floor/kegel exercises three times a day for a few weeks and see if it will improve things. This is just a guess, though, and I'm not a medically-trained professional. Get this checked by a specialist.
With regards to the testicular discomfort, ask your GP to do an ultrasound. I say this a lot, but it's one way to ease your mind and have a better idea as to what's going on in there. Testicular discomfort that lasts for more than a few hours isn't something to just ignore. Insist on getting a full work up!