How to stop insecurities after cheating?

I've been on and off with my relationship for 3 years and there was emotional infidelity on his part and possibly mine too. But we've always found ourselves back to each other. My reason for my infidelity was because I felt miserable in the relationship after finding out how he's been talking to girls and repeatedly flirting with them, obviously this led me to find comfort in talking to other guys too. Which this wasn't a good thing that neither of us did. He was remorseful after we had broken up for 6 months and he has continued to prove that he's changed and proved this by giving me access to his social accounts if I was ever in doubt. I don't like to his access it even when I am having doubts because I want him to have his privacy. We've been together for 7 months now and we've changed for the better.. a lot actually but everytime he talks to another girl - I get extremely jealous and overthink about the past. I often try to control my emotions because I don't want to be petty about every single thing, because when I do ask him about him talking to another girl - its nothing, it's just friendly conversation. I feel like I always have my guard up when I see him with other girls and it's unhealthy, I want to be able to move on with it because he never has need to be suspicious when im talking to other guys and it makes me feel shit that I can't do the same thing. Anyone have advice? or some kind of wisdom?