Thank you for the additional information.
The most likely cause of these symptoms is chronic non-bacterial prostatitis, but is also called chronic pelvic pain syndrome, because it can cause symptoms that are beyond the prostate.
It is good that you had a recent repeat evaluation, because it is important to be certain that there is no infection present, because there also can be a chronic bacterial prostatitis, and the bacteria can spread into the tube that drains the testicles. A chronic bacterial prostatitis that lasts this length of time is less common than acute episodes of prostatitis, but it is important to identify when it is present, as it can be treated with a prolonged course of antibiotics.
The underlying cause of chronic non-bacterial prostatitis is not clear. There appears to be some amount of irritation of the nerves that serve the male genital tract. There also may be some spasm of the muscles in the tubes or at the base of the bladder. Although many men have a similar history to you and notice that it seems to have onset following an initial infection, this is not always true.
There is no single test or combination of tests that prove that this is present, so the diagnosis is usually made by excluding other conditions.
There is no easy treatment for this that will simply eradicate the symptoms, but there are several treatment that can be tried. Alpha-blockers are medicines that help the muscles at the base of the bladder relax and are frequently used in men with chronic prostate enlargement. Alpha-blockers can help ome men with chronic non-bacterial prostatitis. it also may help to use medicines that help to ease nerve pain in other locations in the body. The most commonly used medicines are certain anticonvulsants, such as gabapentin or pregabalin, and certain antidepressants, such as amitriptyline or duloxetine. There also has been some use of physical therapy or biofeedback to help relieve symptoms.