Affair of the Heart?

Today I am sick, so sick to my stomach because I have discovered what I believe to be an affair of the heart. Now I am somewhat clueless in this realm because it's not something I am familiar with; so given this new knowledge that TG might be more than likely is having an emotional affair with a past ex, what do I do?

Maybe some of you are more knowledgeable about this type of thing and can offer insight because all I have done, aside from feeling like I'm gonna vomit; is google emotional affirs. Here's what I have found:

6 Signs of Emotional Cheating

An affair of the heart happens when you:

1. Discuss your partner and relationships with your “friend.” You share your fears, hopes, and dreams (this is emotional intimacy). Which TG has done with Minxie (that's what I'm calling the lying tramp from his past); he has discussed our relationship with her!
2. Meet your “friend” for dinner or lunch without telling your partner. He has never done this, but then again she does live 16 hours away.
3. Keep your computer, files, and internet sites password-protected. I don't know if he has done this because I haven' checked. Should I?
4. Hide or are secretive about your life, relationships, and activities. He is secretive about his thoughts and feelings, and I now believe he shares them freely with minx but not me.
5. Keep your partner waiting while you spend time with your “friend.” Again, see #2
6. Stay in regular, intimate contact with ex-boyfriends or ex-girlfriends. Emotional cheating can spring from close relationships with past lovers. Yes, this is exactly what he is doing! She is an old "friend" from middle school who he dated in high school, and loved for years even while he was married to his ex.

Let me give you some basic background info and I'm sorry if along the way I ramble because I am trying to sort through this in my head while translating it to my heart, so that I can get rid of this sick feeling in my stomach. Minx and TG have known each other since they were children (10-ish) and they dated for a while in junior high and have kept in close contact through the years; all during his marriage to his ex and her two marriages (Minx is working on #2). During TG's marriage he admitted to me he loved Minx but was committed to his marriage and Minx had feelings for him; these never culminated in to anything because he was faithful to his wife. After his separation he went home for a visit and spent time with Minx; keep in mind she's married with 3 children, and they had a brief encounter with one another. They didn't sleep together, but they did kiss and were having what I would call an emotional affair at that time; she mailed him photos of her in lingerie! Bet her husband doesn't know about that!

To the best of my knowledge this ceased over a year ago, but recently I have discovered TG has been communicating a lot via text messaging with Minx. Before you raise the question; how do I kow this; I'll tell you I discovered it on my cell bill; which I have put him and his children on. 209 texts exchanged in 5 days!!!! Is this inappropriate? It feels wrong and a violation of our relationship.

What to do, what to do? I am sick...