Pain when urinating?

Yes hey,

It sounds strange but I've had pain when urinating for the past three years and I know that I often have flakes in my urine. I've already been to two urologists and given constant urine samples but everyone says there's nothing wrong. I've had a prostate exam and an ultrasound scan. None of them turned up anything. I also often had days where I went to the toilet and afterwards my urethra burned and it stayed that way for a while. I've had enough of it, so my doctor gave me an antibiotic. I'm testing it and hope that it helps me. If anyone knows what it is, I'd be grateful for any advice. If the antibiotic doesn't work, I'll go to a neurologist.