Prostatitis: This condition, which is an inflammation of the prostate gland, can cause pain during urination, blood in the semen, and increased frequency of urination. The symptoms presented are classic for prostatitis, especially the combination of pain and urinary symptoms.

Urinary Tract Infection (UTI): While more common in women, men can also develop UTIs, which can cause pain during urination (dysuria), frequent urination, and potentially hematuria (blood in urine), though blood in semen is less common.
Benign Prostatic Hyperplasia (BPH): An enlarged prostate can cause urinary frequency, urgency, and potentially pain during urination. However, blood in semen is not a typical symptom of BPH alone.
Urethritis: Inflammation of the urethra can cause dysuria and frequent urination. If the inflammation is severe, it might lead to hematuria, but blood in semen would be less common unless there's associated prostatitis or other conditions.

Prostate Cancer: Although less likely to present with these exact symptoms initially, prostate cancer can cause urinary frequency, pain, and potentially blood in urine or semen, especially in advanced stages. Missing this diagnosis could be catastrophic.
Testicular Cancer: While primarily presenting with a testicular mass, advanced testicular cancer can metastasize and cause a variety of symptoms, including back pain that radiates to the groin, which might be confused with urinary pain. Blood in semen is not a common presenting symptom but could occur with metastasis affecting the prostate or seminal vesicles.
Kidney Stones: Can cause severe pain (renal colic), dysuria, and hematuria. While blood in semen is not typical, the severe pain and potential for infection make this a critical diagnosis not to miss.

Schistosomiasis (Bilharzia): A parasitic infection that can cause urinary symptoms, including hematuria and potentially pain during urination. It's rare in areas without endemic disease but could be considered in travelers or immigrants from affected regions.
Tuberculosis of the Genitourinary Tract: Can cause a variety of symptoms, including pain during urination, frequent urination, and potentially blood in urine or semen. It's a rare condition in many parts of the world but should be considered, especially in high-risk populations or those with exposure history.