My cock is ~18-20cm. Since I am out of puberty for a long time, it is not as hard anymore and not as long anymore.
I feel comfortable with it, for most of my gfs I was above average on size. Since I masturbate and write stories for myself I am usually a pretty horny guy. When my wife and I have sex, which happens rather rarely I try to warm her up very slowly. I love massaging her pussy, something she really likes.
She doesn't really like giving blowjobs, or receiving felatio. She sat on my face one time and came rather quickly, but then told me that she doesn't really want to repeat that, although I was highly turned on. When I after some finger orgasms, then have to perform it takes rather long. It's not as hard as it was, for > 1 Year we had to stop because I couldn't keep up the errection.
This was a very difficult time for us, my wife even asked me if I'm not turned on by her anymore.
After some time it worked again, but this anxiety never left me. For me the ideal scenario would be to come quickly, I would so much love to come really quickly for her, and her appreciating it, knowing that she can turn me on to a certain point where just a few strokes and a smile would be enough to send me into space. It wouldn't be humiliating, it would free me from my anxiety