Prostatitis and BPH are similar. How and when were you diagnosed with each?
I'm not here to convince you to take Flomax - that's a decision only you can make. I just want to make sure you have all the information. Depending on the dose, either .4 mg or .8 mg, only 8.4% and 18/1%, respectively, of men experienced any ejaculation issues. Again, depending on the dose, 14.9% and 17.1% experienced dizziness, respectively. http://products.sanofi.us/flomax/flomax.pdf (Click on prescribing information at the top.)
Those are real concerns, though. My dad took Flomax, and definitely had the dizziness issue, which is a result of blood pressure changes. He was 30+ years older than you, and had prostate cancer, so your experience may be very different.
I don't know if you have prostatitis or BPH, or both - https://www.healthline.com/health/enlarged-prostate/prostatitis-and-bph That's up to the doctors. Has anyone been able to examine you or do any blood work or anything?
A lot of men here have reported improvements in chronic prostatitis by stopping caffeine. That seems to make the most difference. It isn't a cure, but it can help.