Check the last dozen or so posts in the other thread.
In case you aren’t up to date, this problem has been confirmed as being caused by muscle spasms in the pelvic floor area. It is an uncommon symptom of a relatively uncommon dysfunction known as Chronic Pelvic Pain Syndrome (CPPS). The treatment is consistent (everyday) internal and external trigger point therapy, daily relaxation/meditation and specialized stretching. Pointless seeing a urologist, you need to find a physio who specializes in pelvic floor therapy who can teach you how to do it yourself.