Some advice needed

I’m sorry for the lengthy venting in advance…

My husband and I have been together for over 18 years total and almost 9 years married. Neither him or I are perfect in the “faithful” category by any means. We each have have our own faults and mistakes, which we each owned up to and worked through. Quite a few years ago we separated but never divorced, and we kinda were seeing other people. Then after a while. We decided to work things out and try to save our marriage. In that sense I had cut ALL ties with the person I had been seeing. And I thought he had did the same. And I had found numerous times he was still messaging her behind my back. And I called him out on it…like why am I expected to keep all those doors closed but you’re not? Anyway, after that things were going well. And the last I heard him say anything about her was that he hadn’t talked to her in so long. So I let it alone. Fast forward to thanksgiving 2021 I had seen on my snap chat quick add this person that made me think it was him bc of how the name was. (This was after he told me he got rid of his and didn’t use it, which I’m not stupid, bc numbers don’t lie) I brushed it off thinking it was just a weird coincidence. Well I have never known a password of his to his phone ever since you could have a password for a phone. He is super shady and will only look at certain things when I can see his phone. I on the other hand do not have a password bc that’s my way of showing him reassurance. But, one day I had an issue with my phone and I asked to use his so he could see the problem with mine. Well it clicked in my head check his phone, and I did, and I found that new snap chat account that he had that woman he was seeing on there. And like one other person. I have been holding this in since right after thanksgiving. So for 4 months I have known they have been snap chatting. And I feel like they have been talking longer than that. They reconnected somewhere and somehow. After everything we have been through, and knowing this is our last shot at saving our marriage. I know for a fact if he found on my phone that I even opened a door to a past guy that caused issues, there would be no talking, no explaining, nothing. We would be done in a heartbeat. Like, I’m not one to say who he can and can’t be friends with, but seriously??? You obviously are hiding it for a reason and you only have 2 people on there and not even your own wife? Not to mention, like he will let his phone lay around, but what does that show me when I don’t know the password and you have all of your notifications off? Am I in the wrong for thinking this isn’t okay? Should I just let it go? It’s been eating at me, and I feel myself get so angry every time I see him on his phone bc my mind automatically goes to that. I wanna say something all the time but I don’t want it to be a fight. And I feel if I do bring it up, it brings up the entire past and then puts a dent in the progress we have been making…my gut just tells me that something isn’t right about it, but then other than him being shady about his phone, things are great between us otherwise…I could just use some advice on which way to approach or not to approach it…thank you :confused::confused::confused: