How to get over insecurities

My husband and I have been together for over 10 years. We've been thru a lot since we've been together. He has a very flirty personality which is fine but we've had some issues in the past of him flirting and talking to other women. I don't think it was ever sexual but they would talk about things they both liked that I didn't. That stopped and we moved on but we have an agreement between the two of us to not message/text people of the opposite sex but he continues to do so. He would keep saying he didn't understand why it was a big deal but we eventually moved thru that too.

Porn used to be an issue too and I always feel like I have to initiate sex. I just can't help but feel like he would be more into sex with someone else.

We've talked thru things before but I just feel so insecure all of the time. I'm a bigger girl and I feel like he's always been into women who were skinny and busty. These are all things we've talked thru and are trying to work thru but I don't know how to get over everything that has happened in the past because I'm always worried something else is going to happen. How can I get over this.