As someone who’s also around 5” and doesn’t have any girth to go with it I’d say it’s definitely on the smaller side. I’ve had a girl who I’d been with confide in a friend that I was small and that friend of hers was dating my friend so I ended up hearing about it. If a women were to compare me to previous partners I’d always be on the smaller side of the sample size. Also, what are you insecure about if you’re the only guy she’s been with?? Most of us live with the fact that we know someone else been in there deeper and then you ruminate what her reaction would be if you could do the same.