Thanks for your query,based on the facts that you have posted it appears that you have been taking Rapiflow for urinary problem .
Rapiflowis a drug that belongs to alpha blockers .These drugs relax smooth muscles in bladder
neck which remains open
During normal ejaculation bladder neck gets closed and sphincter urethra
gets relaxed, this facilitates passing semen in urethra and prevents it from going backwards in bladder,
Where as when you take Alpha blockers your bladder neck remains open resulting in semen entering in to bladder instead of entering in to urethra .That is the reason you do not ejaculate semen per urethra.This is called as Retrograde ejaculation
Since semen gets diluted in urine you can not see it in urine however this can be confirmed by presence of sperms in urine if urine analysis of urine passed after ejaculation.