So basically, I'm around 6.5 inches (17 cm) length-wise and around 5 inches thick down there. From what I've read on experience of people with similar size on reddit and various scientific studies, I get that I am on the bigger side, since average is somewhere near 5.5 inches. But prior to knowing this information, I used to think that I'm below average due to what was portrayed in porn and due to my own body image issues, which I still have. I feel better and more confident about my size.
However, just a month ago, I started having sex with my new gf and I can't get over the fact that she might think I'm below average. She hasn't said anything though. It's because, she has only had one partner before me; so all she knows about dicks is from porn. As a girl, she wouldn't have gone to such lengths as we do to research about what's non-porn penises look like. It does make me under confident with her.
To make problems worse, I get stuck with these thoughts while having sex, which makes me lose erection. And this exacerbates the problem even more because I am not able to reach my full size. I keep getting stuck in this anxiety loop.
How do I deal with this? I overthink a lot.