My god!! No wonder some guys perceive all women to be stuck up perfectionists.
There is nothing, and I mean, nothing wrong with sleeping with a hooker. If you can afford it go for it. There are a lot of guys out there that for whatever reason are not in a position to have a relationship so what are these guys to do? Would you prefer they went out to clubs to pick up chicks for one night stands? Prostitutes (in areas were it is legal) are regularly tested for STD's, and do not perform without a condom. Much safer than picking up randoms and less awkwardness if you ever see them again when out with a future partner. They also wash after everyone they have been with so not only are they clean of STDs they are quite literally very clean.
OP, how bad is the guilt eating at you for your fib? I don't think she needs to know, but if it's going to drive you mad and distract you then tell her. She won't be impressed, and she may actually break up with you for it. She may see it as a sign of if you can lie about this, what else can you lie about. Do you really want to break that trust over a little discrepancy? And honestly, that is all it is.
PS My hubby had only been with a handful of people before me. We discussed it early on. I asked how many he had slept with, he said 7 (I think that's what it was... that's how little it matters) and I asked straight up "Did you pay for any of them?" and he said "a couple" and we left it at that. Maybe I'm cruisier than most women about it but I really didn't care. Maybe it's because of where I live (The nearest city is known for Porn, Prostitution, Politics and Pot. 10 point for the first person to guess where that is).
'People are never perfect but love can be. People waste time looking for the perfect lover rather than creating the perfect love' - Princess Leigh-Cheri from Still Life With Woodpecker.