Oh no :( Posts like this actually make me so sad. I'm so sorry this happened to you, friend. I might suggest just being up front with him about this. I try to be positive when it comes to this sort of thing and hope for the best - I try to always see the best in people but, based off all that you said here it doesn't look too good.

What he's been doing is something that's more than just a fishy situation. I think you should talk to him about it, since ya said it's what you want to do. Do what you feel is the best thing to do. If you feel like you want him out of your life you have every right to make that decision but I feel like with this kind of thing it's best to talk about it.

“Paul and I FaceTimed last night, I know you weren’t with him” as another commenter said, simple but real effective. I might also include that you were worried if he was okay. So he knows how much you cared for and about him and maybe he'll realize what he lost.

The fact that it's been several months of this is what bothers me, and that there have been SEVERAL occasions of him staying at her place and this being an ongoing, currently happening thing rather than a one time thing or a mistake - really ruffles my feathers.

I always try to be understanding as we're all humans and make mistakes but he's making it hard for me to do that. He's doing this purposefully, it seems.