Hi, writing this out makes me feel foolish.

My soon to be husband has been secretly messaging other women inappropriately in the last year and maybe longer.
I found out last night from my best friend that he was sending her messages about her ass and having a threesome with her involved, she told him numerous times that he was crossing the line and to stop, apparently this happened sometime in the last year.

When I told him his reply was "this sounds selfish but I am relived that you now know and I will do anything to not lose you"..

Throughout our relationship he's always been paranoid that I've been doing things behind his back when this entire time I find out he just has a guilt consious.

I gave him ONE LAST CHANCE and a time frame of two weeks to talk to someone about his issues. And if anything else comes up I am gone.
I feel embarrassed and betrayed but I do love him and want to work on things.. and just so you all know we got engaged last January.

I'm writing to ask advice if I am doing the right thing here by giving him a chance or am I being ridiculous?