Ok Rachael - Take a deep breath. All decisions should be made from a place of strength, not panic.
It's understandable if you feel you can no longer live with the deception. We all have our bottom lines and dealbreakers. BUT - even if that's true, that you have a reached a point where it's no longer tolerable - you want to breathe deep, think hard about your objectives, and then figure out what will get you the best result.
For example - if your goal is to shock him into reality (a dicey proposition, but sometimes successful - you shouldn't undertake it thought unless you're truly prepared for him to leave) - then fine, confront him with your evidence and ask him to pack his bags. Or better yet, greet him at the door with his bags already packed.
OR - more calmly - you could simply state, quietly and calmly, that you know he's still talking to her, and you don't plan to have any more unprotected sex with him because you don't want to catch any diseases from her.
Either way - are you ready to do this? Or do you need to get some financial ducks in a row first? Squirrel away money, visit a lawyer to learn your rights, make copies of all financial info and tax returns?
On the other hand - if your goal is to simply be done with him, if you have decided this is not acceptable behavior - consider whether it would be in your interest to keep your decision to yourself for a while so you can straighten out your financial situation.
Also - DO make sure you are absolutely sure of what's going on. MAke sure you're not jumping to the wrong conclusion (it sounds like you've got good evidence, but just be sure).
