Brief Answer:
Could be due to Prostatitis.

Detailed Answer:
Hello
Thanks for your query,based on the facts that you have posted it appears that you have ejaculated brown semen.

I shall be happy if you can post me few more details to help me in making comments on your problem.
1) Do you have other urinary symptoms associated urinary symptoms like frequency of urination .poor stream,urgency,nocturnal frequency etc that suggest Enlarged Prostate which is common at this age.
2) Are you taking any blood thinners like Aspirin?
Passing brown semen is mostly due to infection of Seminal Vesicle or Prostate and needs to be confirmed by clinical and digital examination by a qualified Urologist and following basic tests.
1) Urine Routine and Culture
2) Semen examination and semen culture.
3) Ultrasound scanning of abdomen and Trans Rectal Ultrasound scanning (TRUS)
4) Serum PSA.

In the mean while start taking broad spectrum antibiotics like Cefexine along with urinary antiseptic like Nitrofurantoin twice daily and urine alkaliser thrice daily.Later on switch on to appropriate antibiotics as per culture report.

The retrograde ejaculation that you get is due known side effect of Flomax.

Further treatment will depend upon the results of these tests and final diagnosis.

Hope I have answered your query ,please feel free to ask if you have more questions ,
I shall be happy to help you
Thanks and Regards.
Dr.Patil.

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