I've only slept with one person and neither of us had experience of anyone else, so I can't really generalise (as any girl that's had previous experience may have laughed her head off) but...
I'm about the same length as you, I suppose. I was ****ing worried about letting her go near it at first because it doesn't exactly have the biggest girth either.
But then, just as it got hornier and we were getting deeper into the relationship, I thought 'screw it, she's my girlfriend and even if she does laugh out loud, sex isn't the basis of our relationship so even if it doesn't please her perfectly, it should at least please her'. And that it did. Perfectly as it could.
Don't worry about it. Just don't go around shagging random girls anyway, there's no point.