If you've stopped punting and are faithful or are abiding by whatever boundaries you both agreed on then your past is your past, in the same way that her past is her past. There's a very good reason why it's often a really good idea not to pry in to each others past sexual escapades.
You're probably going to have to sit her down and have a really uncomfortable conversation with her. The reality is she's probably got numerous horror stories running through her head about how all escorts are riddled with diseases, they're all forced in to sex work and any bloke he sees escorts can never be faithful, will blow all his money on sex and is some kind of misogynistic monster. If you want to stay with this woman you're going to have to do a lot of listening, talk about her fears of what will happen in the future (if you've only punted whilst single that will help a lot, if you're a serial cheat you're probably fucked all ready). You may have to be very clinical when she probes you on what you did, keep it straight and simple. You may have to be blunt about the sexual health risks you faced and agree to have an STI test to prove you're clean (6 months since you had any sexual contact with anyone).
Don't put any blame on her. You dropped yourself in it by not shutting up. Even if at some point she jokes about it don't treat it as a joke, it's her defence mechanism. Don't fall in to the trap of having her pump your brain for things escorts did that she doesn't do that you like, it's another double edged sword.
Good luck, but for fuck's sake don't get pissed again if you can't keep your mouth shut.
This is sound advice, but only applicable IMO if you think she's a keeper (or you're married) and you want to invest the time to repair the damage.
I get the sense she feels cheapened since she's done what dirty hos previously did for you. Unless your relationship ends up being very strong, this will always be lurking and I think you can forget about her ever giving you a dirty massage again.
You need to get it out into the open and clear the air. It's an easier ride if you at least take some ownership of the direction of the conversation rather than having 20 uncomfortable questions fired at you which might sink you. Personally I'd offer lots of information (breadth) about when you went, why you went, your state of mind and what happened. Your call how much you actually divulge about what went down (no pun intended). It's not clear exactly what you've told her already but there's a difference between going a couple of times when you were single some years ago because you were curious and going twice a week for many years, even through previous relationships.
So... be open and "honest", say you don't do it anymore, say you want to be with her, allay her fears, understand why she's feeling the way she is, make her feel valued, ask her what she wants from you and how you can rebuild the relationship because you're committed to it, or... just move on.
