Failing marriage?

I'm 21. Husband is 24. Just got out of active duty marine corps last year. Anyways...

I have a lot of insecurities about myself even though I have a nice body. He tells me all the time how gorgeous I am, etc. but I can't seem to get over how many women he has slept with. Over 40! I've only been with 4 men. Plus, he watches porn every single day. It just makes me feel like he has to look at other women to feel satisfied. His ex girlfriends and one night stands were for the most part really pretty and I feel like I don't measure up. Obviously he married me, but it's becoming a huge insecurity for me every time I think about it. It gets to me so bad I withdraw myself from my husband because I feel so crappy about myself. I always wonder if he wishes I looked like one of the girls he used to sleep with. It just tears me up every day. I can't live like this. Please no hate, I just want words of advice for how to cope with these thoughts. I've always had anxiety and insecurity.