Sperm (General; Miscellaneous)

I was looking for some unimportant medical information on a Dutch general practitioner website, and they have a question forum.* **
I looked at the headlines and this one caught my attention. Weird, and I would be quite worried:

* Here laypeople seem to give each other medical advice, and I find that a bit weird.
** Note for mods: This is from a publicly accessible forum, without any access control or passwords, so I'm not revealing any private information!

I, male, have had blood during urination after ejaculation (masturbation) for a year now. Don't have sex with anyone else.
Went to the doctor last year with it and submitted urine where blood was also clearly visible to the naked eye. I was told it was a bladder infection.
After a year I still have blood and pain with urination after ejaculation. If I have stopped ejaculation (masturbation) for between 2/3 - 8/10 days the bleeding is completely gone and there is no more pain. Moment I start ejaculation (masturbation) again the bleeding starts again at the first/second peeing with the pain added.

The bleeding only occurs after ejaculation and not during or at the time of ejaculation, which otherwise looks completely fine.