Why does this affect me so much now and how can I overcome it?

Hi, I (38M) have been suffering with RJ since earlier this year and it’s led to some major problems in my marriage. When I get stressed and anxious it’s all I think about and it leads to further problems and arguments.

It started after child number 2. My intimacy with my wife dropped off a cliff much worse than after child number 1, which is understandable. I foolishly tried to work on this by suggesting ways to spice things up or talk more about sex and ideas we could try. This led to a conversation where she revealed she’d had anal sex with a previous partner. Something I’ve never experienced.

I’d never directly asked her about this before, but she’s always implied it was off the table and not something she would do. So I just assumed she never had.

What has followed has been a good amount of arguments. Making the mistake of asking more questions and never feeling better about any of the answers. She became quite defensive and just said I have no right to know about her past.

What’s strange is before we got married she revealed to me that she’d had a ONS and caught an STI. She was worried that it would be the end of the relationship to reveal this to me. However, at that time I remember being completely unbothered, laughing it off and supporting her and telling her it didn’t change anything.

What has happened to me now? Why have I changed, why has further information caused me to ruminate and think about things constantly? Obviously there are big differences in our life since then, being married, having kids etc.

I fully accept that this is a me problem, a mental issue that I want to move past and learn to deal with. I’ve watched a lot of YouTube videos and read posts on here to try to get tips.

I’ve tried self improvement and did manage to have some success with weight loss and building strength etc.

Does anyone have an insight into my situation and any advice on how I can improve things? I appreciate you for taking the time to read this.