Rickard,
My understanding is that the seminal vessels are cut and sutured
a short distance from the testicles and this is the "short tube" that gives part of the sensation of ejaculation during the sensation of orgasm for the radical prostatectomy patient.
My physician suggested (not from a direct question) that the sperm that travel to this destination die there and are absorbed by the body. I'm not certain but "death and absorption" is likely the fate of any sperm produced that are not involved in this aspect of the sensation of orgasm that are left in the testicles as they are still produced and die.
(Any ascetic monks or celebate priests here to give insight?)
As for your sensation of pain, I am not certain what is the cause. The locus of pain you describe (away from the testicles) suggests it is internal sutures being over-exerted for their state of healing. This possible over-exertion might be from the frequency of orgasm and/or the activity that produced it.
Even though you had very little problems with incontinence and ED - and it has been seven months or so since your surgery, you still have a lot of of physical trauma in the pubic area from the extensive surgery and your body has a lot more healing to do!
Try going slower for awhile. Make a notes of the frequency of sexual activity and the sensation of pain.
Maybe start a stomach-crunch exercise routine that focuses on both the internal lumbar muscles and muscles surrounding the pubic cavity (The pubic cavity is surrounded by "lower abdominal muscles" and pelvic floor - i.e. kegel - muscles) and
slowly increase your level of exertion. Don't hurt yourself!
If you had discomfort at twelve hours, try waiting twelve and a half hours! 
I'm sure you will be fine.
It is good to hear from you. Has your golf game returned?
Taksameka!
CCedar
ICTHUS!
Rickard Wrote:
...I can feel some small not paint but almost in left part of stomach... I connect this with the ejaculations and the the short tube is filled and the body needs time to empty it before next try....