Advice - My first non monogamous relationship but not my partners

So, first, for context: Me, 32 yo, have had 3 monogamous relationships. My parter, 31 yo, have had maany relatinships in life, most of them were non mono relationships.

I started considering myself as a non mono person, and started dating my current partner (we’re married now, been together for 5 years) Our relationship was always non mono, but at one point i started getting reeally low self esteem and the thought of my partner being with someone else really brought out these bad and paranoid thoughts and feelings. We decided to be mono for a while and that was fine until my parter wanted to go back (which i can understand) and we talked, layed some rules and etc. Due to my low self esteem ive really retracted from having sex, bc im afraid to take my clothes off, dont feel very comfortable or sexy enough and we’re working on that, things have gotten better but now my partners feels like she wants to flex the rules bc shes starting to feel not like herself anymore and i get that. I confess i havent been dealing with my process of becoming a non mono person as i should, and i want to feel better about it, work through the jealousy and the paranoid thoughts. My self esteem is still reeeeeaaaallly low and i feel reeeeaaally bad about myself and how i look, but im working on it, been doing my exercises, eating healthier, working on getting some therapy. Trying to love myself more here so i can love my relationship and my partner like i want to.

But i could use some advice from someone that maybe had a similar experience (being the fresh non mono and ex mono person with a seasoned non mono) and/or is a person with low self esteem.

How to deal with the jealousy, the paranoid thoughts, the awful feeling of being afraid of maybe losing the partner for someone else, what if the person they go on a date is better looking than me, idk there are a lot of things to deal and i could really use some advice lol