Also, we have a shared cell phone account in her name. We don't get detailed billing, but I can look up call records online. And I have checked all the way back to October and don't see anything unusual.
Texts are a different though. I can only see the number of texts delivered. So what I do is keep an count of the number of texts and compare that with the texts she sends me. The count may be off by 1 or 2 a week. And when the number are way off (more than say, 5), she'll usually say something like "I got a text from my mom today". Could she be lying? Possibly. But she doesn't know that I am checking. So it doesn't make sense.
Good deal -- I'm glad you're checking. She could however be texting internally thru another app (ex.: you can text with people you're playing with in Words With Friends), and it's also very typical that cheating spouses have 2nd "affair phones" (usually prepaid). Just keep your eyes and ears open; of all the things you reported to us it was the "suddenly treating the kids very coldly" thing that jumped out the most.
Can I ask you a personal question? Are you guys still ML? If so, does she kiss you on the lips? Does she kiss you on the lips even OUTSIDE of making love?
