Partners ex’s

So I’ve been with my girlfriend 4 years,  I’ve always had a but of a problem with jealousy,  but in my opinion only where its justified.  My girlfriend is still close/in contact with multiple ex partners. I know she would never cheat, but she is always liking and commenting on their social media pages and visa versa, I know its harmless but it still bothered me and she knows this.  I think im bothered by it more because I am not close with an any partners. I dont want to control her or stop her from feeling like she has her freedom,  but I know I wouldn’t be liking my ex partners pictures and stuff if I know it bothered her. It doesn’t help that all of her ex partners are older and better looking than me.  I know I’m an insecure guy,  and I don’t want to bring up the issue with her again,  I just cant stop comparing myself to her ex’s and its making me super depressed.

Am I the only person who feels this way and what can I do to help this situation?