This is what I was thinking as well. He may have not meant what he said in any negative way other than his explaination, but you don't know for sure. I imagine if he's a good guy that you want to stick with, he'll be appreciative of your openness and willingness to be vulnerable to him by showing him the pictures. If he's going to be bothered by what he sees in those pics, better know it now than after your body inevitably changes as you get older, have children, etc.

Seems like a good oppurtunity for your relationship to grow!