What does your gut instinct tell you? Whatever it is, go with this. And if it means the end of the relationship, well, it's best that you find out now rather than after you are married.
it doesn't sound good, but without knowing you or your partner it's hard to know the full picture/context etc.
its not an easy decision, good luck!!! Xx
I don't mean to sound harsh but I think you should be very wary. What does he mean by a guilt free week? Have you confronted him about it?
In my opinion the fact that you feel the need to check his messages, and the fact that you have found these both are alarm bells to me.
You need to have a chat with him before any wedding, as you say marriage is a big commitment and certainly shouldn't be taken lightly with the thoughts of "do I trust this person". As much as some people have several marriages trying to find the right person, I think it's important to see this marriage as "the one" otherwise why waste your time with something you know won't work?
Again, I don't mean to sound harsh I just think that this is something that should be ironed out well in advance of your wedding. I know if it was me I certainly wouldn't be happy.
Hope you get things sorted! Xxx