I've never had sex with a real girl, only with escorts. should i pretend that i'm still a virgin?

Not telling her or lying about it would be a horrible idea. Since relationships are built on trust, breaking it on something that important would destroy the relationship. Instead, you need to just admit that you had sex before. You don't have to say that it was with hookers, you can claim one night stands or drunken mistakes or something. But do be honest on your experience and, if she asks, number of partners.