I think most of us snooped at one time or other, I know I did. I found it was like opening Pandora's box, it always hurt me in the end.
That said, you know what you know and now it's time to decide if this relationship is bringing anything good to you, and if it is healthy. If not, as sad as it will be, it may be time to live on your own. Lonely is better that doubled over in pain, yes?
My heart goes out to you, I know this hurts.
Hugs