Cheating?

Hi guys

So yesterday my partner was asleep and I took a photo of us and applied it to his wallpaper. When I swiped up to remove the tab I noticed an Instagram page... a new one he had set up without my knowledge!! I clicked on it and it was full of half naked girls and a girl who he used to fancy and nearly had sex with during our 2 year breakup!! I went on to messages and the only message was to her asking for her only fans link and asking what content she posted!! I woke him up and told him I was done with his shit as it's not the first time his done this... he done it twice or more that I dont know of when we were together before we split up!! He has no excuse for what his done and says his sorry!! I have tried so hard to trust him this time and when I finally got to 100% he does this and now I'm back to square one!! He asked me to marry him over a year ago now... I took my ring off as soon as i saw the message and the new page... he says his an idiot which is obvious.. the thing is I'm not even upset or hurt I'm just angry!! I dont know what to do I live with him and his parents!! This girl is so much prettier than i am and it's making me feel so insecure and that I'm not what he wants even though he says none of that's true!! I have suffered with anxiety and depression and really dont want to get back to my worst ever again!! I'm a lot stronger than before but I'm still in two minds about leaving or not 😒