There's so much I could write. I'll try to paraphrase. I've been in this position twice. One is ongoing.
Knowing and demanding someones sexual history is not the same as knowing if your man has ever paid for sex. Nor is it like porn (and I don't like that either). The majority of women would prefer their partner not to have paid for sex. Ever. And if they had, to know this so they could exercise choice; either way. It's fine not to be bothered if you really aren't. So I think people conflating these things isn't helpful.
I was in a similar position in the past, told about sex workers in their past, let it go (against my instinct) and it ended very badly a couple of years later.
I'm in a relationship now (over 4 yrs) and have the same issue (I have had relationships in between where I am pretty sure the men never had done this!) - although we aren't married or cohabiting. Found out 8 months in, when madly deeply in love. Had I known before - anyway, but esp with my history - I absolutely would have passed. Hard pass. So what do you do then? I carried on what is/was an otherwise satisfying and loving relationship.
Anyway. It hasn't gone away. Most of the time I have forgotten about it. Every few weeks/months it rears itself despite my best efforts. I've had counselling. We've had one session together and I am prepared to do more but I do wonder (him too) if it is vain.
I love this man. He's been my best friend and confidant. However, I can only explain that it's been like trying to suppress something integral to me. There's other things too... porn (recent past), strip clubs (distant past), sexist comments on social media (mid past), and a few things he's said as a joke (in our relationship) that I think... wow! Ultimately, he is not a feminist. I think most of his exes have been pretty liberal so maybe he didn't see the issues. He does regret what he did now, claims it was just peer pressure/curiosity (he was 30 not 18 though), and says he's stopped using porn. However in arguments sometimes things come out that seem to justify sex work etc. I think I can probably only realistically date men that are feminists - in deeds not words. And not - at my age - that need educating about it. Fuck that. He can think what he does (and I am sure if we split up which seems likely that he will think I've been over the top and unfair) and I can think what I do (that sleeping with sex workers is not an attractive trait or a positive sign in a serious partner).
It's an awful awful situation. He's an otherwise kind, loyal, sensitive, connected and fun boyfriend. Swept me off my feet. In a good way. I am mostly heartbroken. But I do feel that we need - as women - to raise our standards when it comes to sex work, porn etc. And maybe, once again, despite my instincts and feminism etc, I didn't. I thought I could let it ride over me due to love and it being before me/a long time ago. However, it is still proving very very difficult.