<human>: Can you condense the text into a few key points?

Fellow weddingplanning redditor here, Throwaway for obvious reasons. Just want your opinion. 

My fiancé & I have been together 4 years and are set to get married very soon.

A few days ago I noticed he had added a girl on Facebook who I knew, but he didn't have any mutual friends with her. I thought this was strange but ignored it.  I normally don't care if he adds girls, but something about this struck me as very odd.

I started noticing him acting funny. Hiding his cell phone, leaving the room when his phone went off, being generally weird. So I did a terrible thing and logged into his facebook. He had deleted all his messages, but I checked his activity log and he has searched for this girl AT LEAST 7-8 times a day. Every day.  

Some how it had logged me into his messenger and stayed on my phone even after I logged out of his account.  Earlier today I (he) got a message from her that said "not right now, I'm in public." 

My face instantly got hot but I couldn't find what he had messaged her. We went to a wedding tonight and I've been trying to act normal but drop hints that I know something.  

A few minutes ago I (he) got a message from her that was just a winky face...

So tell me reddit. What would you do? Call him out? Call off the wedding on a hunch? Or just let it continue? 

thanks.
<bot>: Fiance may or may not be sexting a girl on facebook. Supposed to get married realllllllly soon. Have no idea what to do.