Talk to Urologist on Pain In Private Part

AssalamOAlaikum 22 years old male here. Whenever I get a signal for toilet and I visit in next 10-20 minutes everything is fine. But if due to some reasons I don't go, an intense pain in the arse starts which stops me at a place and I'm not even able to change my position a bit. Sometimes I even have to place my hands over my bum to reduce pain (which is obviously of no use) and it's awkward. So far, I'm lucky that I haven't experienced it in public but I'm afraid that I can face it in public. Kindly note that at the time of poo there's no pain at all in any situation and no constipation or bowel issues at all. It appears only at the time of signal/ urge and experiencing it since last year approximately.

Any findings? Recommended tests etc.