Husband dropped a bomb

I want to preface this by saying I have pretty bad anxiety. I am posting this with the main goal of finding out if my concerns are founded or all in my head.

My husband and I have been married since 2009. In 2012 I found out that he had an app on his phone and had been talking to several women. More than 40.

I was devastated, and to make matters worse, we had a newborn daughter. The app didn't log conversations, I only found out because I was nursing our daughter one afternoon while he was sleeping before work (he works nights) and his phone vibrated that he had an email, and it showed the headline with the womans name.

I immediately woke him up, asked him what it was. He denied it. All involvement. I sent out messages to each of the women but none of them ever responded, even the one that had just messaged him. I never got ANY closure from this. He insisted that all he ever did was talk to these women because he was "lonely".

Fast forward to tonight. 99% of our relationship is amazing. He is a great father, works hard to support his family, is supportive and helpful in all aspects of my life. Seriously, the best. And then things go to shit.

We are laying in bed in a post coital haze and he mentions a blowjob to get himself revved up for round 2 - this makes me think of something I had seen on youporn, and prompts me to ask him if he watches porn.

In all the time we have been together, he always swears that he never watches porn. I never ask him to trap him, I'm 100% ok with it (obviously, since I watch porn myself) but he always denies it and we move on. Not tonight. He says yes, and I immediately get excited.

I start with all the questions I've always wanted to ask him. Which site? When? What's your favorite kind to watch? How long? I am giddy and ready to delve into this new facet of our relationship, but instead he gets defensive.

I back off and just let him know it's not a trap or anything, and that I genuinely am just excited to learn more about his preferences and him and bond over this newly shared topic. This leads to me asking a new question after a few minute of silence - have you been deleting your browser history?

This is a big one. Ever since 2012, I have been the one to delete his browser history. It gives me comfort to be able to look through it whenever I get nervous. It isn't often, but it had happened recently enough that if he had been watching porn I should have seen it.

He says he uses a private tab that doesn't log any history. Ok. I didn't know that was even a thing? He tells me he has been watching porn for 6 months, and answers all my other questions as well but we will skip that as this is getting long.

I cannot get past the secrecy. 6 months is a long time to keep this from me, I literally tell him EVERYTHING and can't even playfully lie to him about something, it just isn't ok to me. the knowledge of this "privacy tab" is seriously throwing me off as well... He says he only ever uses it for porn, but now I can't stop thinking about all those women from 2012.

I am so anxious about this I can't sleep. Am I crazy?? Should I let this go?? No big deal, huge deal? I'm not sure if I'm making this out to be more than it is.

Am I letting past hurt cloud my judgement? As far as I know all he did then was talk to them online through the app and has never made any other mistakes. The paranoia, the feelings of doubt, the self esteem issues that I got from this... none of that has ever gotten better.

Am I making a mountain out of a molehill?