Do I have urinary retention? Should I get a cystoscopy despite "normal" tests?

[BenBilly]

Hi, i'm a Male, 42, lean physique

My question is where I should be concerned about what I consider "urinary retention" and whether I should get a cystoscopy based on my already-performed test results.

For 5 years or so, I've had what I consider some minor issues of urinary retention. But it doesn't cause me major discomfort. It is only problematic before sexual intercourse.

Whenever I urinate, I do sense there are few more drops (up to around 20 mL) that haven't come out yet. Generally, it's not a problem. It's not really uncomfortable.

BUT, whenever I am about to have sex with my partner, I need to excuse myself to go to the bathroom because I do not feel I can proceed to ejaculation without shaking out the last drops remaining from my last urination. Sometimes, 2 trips are required.

It wasn't always this way. There was a time when I could just go to the bathroom and then I could have sex a few minutes to, say, a half hour later. But, now I always have to go the bathroom *right* before sex.

Typically, I need spend half a minute shaking out between a few drops and  20 mL of urine. Then, I can proceed.  

I have seen a urologist.
A digital exam of my prostate seemed normal.
A rectal sonogram seemed normal.
I did a urodynamics test and the lab tech who performed it said I voided everything normally (though I haven't discussed the test with the doctor yet).

The urologist had scheduled me for a cystoscopy but I cancelled that. I have heard how painful and uncomfortable that can be and I'd like to avoid it unless it is highly recommended given my symptoms.

So, do you think I should proceed with that cystoscopy, even though my urodynamics test was deemed "normal"??

Again, what I usually have to void is only a few drops to around 20 mL.