Good news.....O ye of lesser girth, take comfort from my experience. My g/f was married for some years to a guy with what she described as a massive cock. But....she never ever had an orgasm with him, no matter how much lube he used, time he took, etc. My cock is just average, 7" max BP, though I do have a large mushroom head, about 6" around the "flange". Overall girth barely 5" around. Not large, just average. And a grower, not a shower, flaccid length barely 1".
But this is not about cocks.
The first time she and I met, sexually, she came several times, just with the two middle fingers of my hand, 3.5", max 3.5" penetrating length, because I was stroking her G-spot with a "come hither" motion of my fingers.
Where is /was her G-spot?
It seems to be the point where the inner "arms" of the clitoris meet the external shaft. i.e., not very far inside the vagina.
Not only did she come, but she squirted genuinely from her vagina (not just peeing during sex).
When we progressed, over the next few days, to penile penetrative sex, she turned out to be multi-orgasmic.
Why?
Maybe she was just more comfortable with a more average sized penis ( as compared with her husband's monster cock), and maybe it helped that I have a large mushroom head, and an upwards curve to my erect cock.
Whatever, she was the most orgasmic woman I ever mat, repeatedly coming in waves of really powerful vaginal contractions, over and over, and frequently extremely wet.
Nothing to do with penis size at all.