Hello.... About 8 Months Ago I Began Feeling A Stinging

Hello.... About 8 months ago I began feeling a stinging pain after I would ejaculate. The pain would go away after 20 minutes or so. I started feeling the same pain on a daily basis throughout the day. Ive seen 2 Urologists who have prescribed every antibiotic possible and nothing has worked. Ive had 2 cystoscopies done and they have found nothing wrong. My last urologist diagnosed me with chronic prostatitis and basically sent me home with no cure. I continue to have a feeling of irritation and stinging in my urethra. This is affecting my work and making my life miserable. Im 38 and have 1 partner last 15 years so I'm 99% sure its not an std or anything like that... Just need some advice on what steps I can take from here