Well, being male, I obviously can only relate from a distance to what I'm well aware of in the department of insecurities around looks etc.
But I CAN offer this.
The deeper parts of a relationship are so much more the glue that binds people than other superficial things like looks, body styles etc. I think we all know this - but selectively forget
Bottom line, relationships aren't (shouldn't be) a competitive sport. There will always be people who we might compare more and less favorably with ourselves on any number of issues but if someone loves us, they love us for the qualities we have. We can't have ALL of them ! And it's a non-issue.
From you're writing I feel you're being unreasonably hard and critical of yourself. Fear will only make this worse. Believe in yourself - obviously HE does
And trust that a shiny new toy can't add any depth that he desires deeply any more than you can.
I would just suggest you not put too much energy into being concerned about physical and sexual attractions. That's just not what's critical in a relationship in the long term. No relationship (that I've seen) can hold together based on sexual chemistry alone. There's other stuff more important in the long run. But that doesn't mean that that sexual piece isn't nice to have at times. It's all in understanding the nature of the beast.
Just be yourself. You're obviously special