The medication you mention is similar to what was prescribed for my husband. All it does is lower blood pressure. You need to try alternative medicines for your prostate troubles. Diet has a lot to do with it. There is much information on the web for natural treatments of BPH.
My husbands BPH caused his weak urine output also. What happened to him was that his bladder was not emptying completely and he ended up in KIDNEY FAILURE due to having too much urine in his bladder.
He was going for yearly check up at the VA clinic. They saw that his creatnine was going up and did NOTHING about it.
He got a UTI and instead of figuring out why they just prescribed Antibiotics and sent him home.
He started to get incontinent and was wearing pads to prevent leakage. I could go on and on but I am sure you understand.
Seek natural therapies and not prescription drugs with their side effects and NO CURES.