Hello,
For such symptoms first of all any obstruction in the flow of urine and semen like in the urethra and prostatitis need to be ruled out.
First of all your symptoms are not the typical symptoms of prostatitis.The typical symptoms of prostatitis are fever, pelvic, testicle, or rectal pain,frequent and painful urination and ejaculation and incomplete emptying of bladder.
I suggest you to consult a urologist and get your PSA levels and a cystoscopy done to rule out any obstruction to the flow of urine and semen.
I hope it helps. Take care and regards.
Plenty of urine? Have you seen a urologist to check your prostate? Has he asked you for PSA test, and the level is normal?