AITAH for reading my boyfriend’s old messages and finding something about his past that I can’t get over?

I’m 23F and my boyfriend is 26M. We met about a year and three months ago and officially started dating about a month after meeting. We are now expecting our first child together, who is due in about 7 weeks.
Throughout our relationship, my boyfriend has always portrayed himself as very reserved, loyal, and committed. Those are qualities I’ve always loved about him, and I have genuinely trusted him. I’ve never had the urge to go through his phone or messages because I’ve never felt like I needed to.
Recently, I was put on maternity leave earlier than expected and needed to scan some paperwork to send to my boss. My boyfriend was at work, so I used his laptop, which he has always been completely fine with me using.
His MacBook is still linked to an old iPhone he had before we met. He switched to a Samsung shortly after we met, so there are a lot of very old messages and notifications on the laptop.
When I unlocked it, a bunch of old notifications started popping up from 1–2+ years ago. I was just clearing them out while doing what I needed to do.
Then I noticed a message from about two weeks before we met. I happened to see the words “massage” and “prostate.” That caught me completely off guard, and I couldn’t help but wonder what the message was about, so I clicked it.
I saw that he had contacted a woman asking about getting a massage and specifically requested her by name, saying he had seen her listing online. She responded with the services and prices she offered. It was very clear that this was not a normal therapeutic massage and included sexual services.
He never responded to her message, so as far as I can tell, nothing actually happened with this particular woman.
At first, I tried to give him the benefit of the doubt. I thought maybe he had been misled by the listing or didn’t realize what kind of service she offered. He’s a mechanic, so him looking for a massage itself wouldn’t have seemed strange to me.
But I was uneasy, so I looked up the woman and her old advertisements. It was extremely obvious that she was advertising sexual services and even described herself as an escort.
That’s when I realized the inquiry probably wasn’t as innocent as I initially hoped.
I’m not proud of this part, but I started snooping.
I searched his old messages for the word “massage” to see if this was something he had done before.
I found multiple conversations with different women where he was asking about 30-minute or hour-long appointments. Some conversations were just attempts to schedule something and never happened because their schedules didn’t line up.
Then I found one conversation that really made my stomach drop.
There was an Apple Pay payment for $150, followed by messages indicating that he wanted to see the woman again. A few days later, he contacted her again saying he wanted to see her and that he was outside.
Those actual encounters happened more than a year before I ever met him.
The only thing I found that happened shortly before we met was the inquiry I initially saw, and there doesn’t appear to have been any actual encounter from that particular conversation.
So I know this isn’t a situation where he was secretly doing this while we were together. Everything I found regarding actual participation happened before we met.
But it still completely changed how I see him.
If someone had asked me before this whether my boyfriend was the type of person who would pay for sexual services, I would have laughed and said absolutely not. I would have been completely wrong.
And now I’m sitting here wondering: What else could I be wrong about?
I immediately texted him. I was honestly sick to my stomach. I asked him if this was something he had done in the past because I needed to know whether this was something I should ever be worried about happening again.
He responded, “Why are you asking me this?”
I told him that I already knew the answer and that I just wanted to see whether he would be honest with me.
He was.
He admitted that he had tried it before, a long time ago. He told me that it was a different time in his life, that he wasn’t proud of it, and that it is absolutely not something I ever need to worry about. He told me that he loves me, loves our life, has way too much to lose, and would never do anything to jeopardize our relationship or family.
He took accountability and honestly said everything I would have wanted him to say.
I told him that I believed him.
But internally, I can’t seem to let it go.
What scares me isn’t necessarily that he did this before we met. I understand that he had a life before me and that people can make choices they aren’t proud of.
What scares me is that I genuinely never believed he was capable of doing something like this.
Some people have certain lines or morals that they would never cross, and I always believed he was one of those people. Now I know that, at least at one point in his life, he was willing to cross that line.
So I keep thinking: What happens if one day he doesn’t feel like he has as much to lose? What if he’s confident I won’t find out? How do I know that the version of him I’ve known for the last year and three months is really who he is?
And then there’s the fact that I wouldn’t have known any of this if those old notifications hadn’t randomly appeared. That’s making me question whether I actually know my partner as well as I thought I did.
I know I crossed a line by intentionally searching through his old messages after the first thing caught my attention. I feel guilty about that, and I know I invaded his privacy.
But now that I’ve found this information, I can’t exactly unknow it.
So, AITA for going through his old messages after accidentally seeing the first message, or am I justified in being deeply unsettled by what I found even though the actual encounters happened more than a year before we met?