I am sorry to read of your troubles. Urinary retention is a horrible condition, making an ordeal of what should be a routine bodily function. I have been taking Tamsulosin for the past 20 years for BPH. The condition is largely under control, with occasional flare-ups of varying intensity and duration. Thirty days ago, I had a biopsy with 20 cores being taken. Immediately following, urination became increasingly difficult until, some five days later, I was in severe pain from urinary retention. Every trip to the bathroom was a 20 minute battle. Thankfully, my urologist heard me and added a daily 5 to 10 mg of Tadalofil (Cialis) to supplement the Tamsulosin, and doubled my Tamsulosin prescription with the caveat that I should reduce at the earliest time possible. Concurrent with the additional medication, I went on a strict vegan diet--absolutely no dairy and meat, and no ultra processed foods. After about a week of the worst symptoms, I was able to go back to my regular dose of Tamsulosin. Now, 30 days later, all of the symptoms are gone, and flow is even better than before the biopsy. This is just my case, and it may provide you with an avenue. I will continue with the vegan diet to see if my improved condition becomes the new norm. They found cancer in the cores, so I know that I will have other challenges ahead of me.
As others suggested, I hope you can find a better urologist--one who can help you with your symptoms rather than defending his own abilities. My best wishes to you.