Am I just being insecure?

This has been happening for a while now. I'll be scrolling through Facebook and come across a picture of a practically naked girl that my bf has liked and it's like a knife to the heart. It's not pictures of his friends that bother me it's pictures of professionals, nude models, provocatively posed, just covered enough to be on Facebook. And they are polar opposites of me with their dark hair, wild make up, lots of tattoos, while I am blond, have no tattoos and hardly wear any make up. It makes me wonder if that is really what he wants.

It also bothers me that it is on Facebook. If I can see it so can anyone else on his friends list.

Am I just being insecure and overreacting? Or do you think this is something I should be concerned about? Thanks in advance for your help.