Does size matter? YES! --- to the owner, anyway.
Didn't mean to scare you... but it's the truth... your penis size can achieve penetration in all but the most bottomless of women. So relax -- there's a reason for average penis size... to accommodate average vagina size.
I am a rather petite woman... and contrary to all the hype... I don't much care for "large" sized men (it's like looking at a train wreck... grabs your attention, but all you can think about is all the pain). A man of average length and girth is preferred. His proportions seem right... it looks good... and more importantly... it usually feels nice (especially if he knows how to use it).
Though, this is simply one aspect of sex... the fact that there is an emotional connection and we share similar "kinks" works to enhance the physical delights. There's more to sex than just sex -- especially for a woman.
Don't be hard on yourself (no pun intended)... stop looking down on your size, and realize the vast majority of women on this planet can be pleased by your size and girth. Any woman who says otherwise either is too small or too big... doesn't know how to enjoy sex... or is being spiteful and using your insecurities about your penis against you.
"The weakest soul, knowing its own weakness, and believing this truth that strength can only be developed by effort and practice, will, thus believing, at once begin to exert itself, and, adding effort to effort, patience to patience, and strength to strength, will never cease to develop, and will at last grow divinely strong."
- James Allen