I knew I was the jealous type, but...?

Okay. Help me possibly understand something. I have had a friends with benefits for 6 months. Tonight he and my friend met for the first time. I didn't realize until then just how jealous and insecure of a person I am!

They hit it off so well and were like "hanging up" against me and teasing me about stuff..like they both do individually but it was so weird how they seemed like instant buddies. I have always been cautious to introduce this friend specifically to any guy because she is good looking...not that I am not, but I mean she has nicer boobs and *** than me (in my opinion). She randomly, out of nowhere, shows me a picture of her plastic surgeon who did her breast reduction. Then started talking about how big they used to be. My fwb jumps on board and is like wow that was big...then starts talking about an ex girlfriend he had many years ago that had big **** and she could basically just show her **** and get him to do whatever she wanted him to do (jokingly). But then he's like oh but she was only 5'2; and my friend is like "I'm 5'2"... yes, I know I am overthinking all this...but now I just feel weird about it all...like he'll want her now or something...

What the heck is wrong with my thinking?

(I divorced my (ex)husband of 16 years just over a year ago...he cheated on me and put me down. )