CaliGuy, mvgfwd2 are right. So am I. Listen to us. We've been where you are. Your situation is not unique in any way. What we've learned that works and what we've learned that doesn't work applies to you to. Please follow the advice given. It'll give you your best chance at either fixing the M or moving on in a healthy way. They key is not to languish in this limbo maybe we'll fix it, maybe we won't phase. She doesn't mind because she has someone to comfort her. The OM. You? It'll possibly kill you. It almost killed me.
My little phone trick? Someone who had been through this before me told me about it. I figured what the heck. I had some minor suspicions about my wife but that was it. I figured no way she was cheating. I thought I'd play this little game to rule it out in my mind.
We left the house and got to the mall. I purposely left my phone at home. I said "crap I need to call ______ <our son>. I forgot my phone, let me use yours." Now, in our lives I've done that legitimately about 20+ times and she had always handed it right over. This time? She first says "I have work stuff on there now and I'm afraid you'll mess it up." I said that's ridiculous, I'm just going to make a call. Let me use it. Then she said, I'll call him, what did you want to ask him? I said never mind. I knew everything I needed to know. That gave me probable cause to snoop deeper and BOOM, there it was.
By the way, today we're still together and have fixed our issues. If I ask to use her for or she asks to use mine, we each would hand it right over.
Not all M's can be fixed. You made a good choice coming here. Now make another good choice and listen to our advice. Be strong. You can do this.