Tell her the real number e.p. (just don't say that a lot of these were escorts) and she'll probably think that you're boasting and won't believe you. On the off chance that she does believe you, tell her that in your younger days you were a bit of a jack the lad, but that you have now matured and feel the need the settle down and put down some roots.

P.S. I hope you're not too young, so that there is a respectable timespan between your "younger days" and the present.

But on the other hand, you could always confess to being a sex addict, but that since you have met her, she has totally changed your outlook.