I am sorry, but he has crossed the line. If he is exchanging messages with a woman, that he doesn't want you to see, then he is having an Emotional Affair. This is my story...
XH didn't like his best mates wife, didn't have her mobile number. Gave her a couple of lifts to Uni, spent some time with her, started talking about her all the time. Felt sorry for her. She cried all over him about the loss of her baby in 2007.
XH walked out on me with no warning Feb 2012, came back, walked out again at Easter.
I then discovered facebook flirty chat, daily emails and thousands of texts a month to this woman. Everything with a xx at the end of it, which he never did to anybody. Sending her motivational emails telling her that everything will work out OK in the end. Claiming that they were just supporting each other emotionally, because her H couldnt support her. He bought her lovely birthday presents, spent the day with her on her birthday. All while I thought that we were working things out.
When a man is texting OW from 8am til midnight all day every day, when its the first thing that he does in the morning and the last thing he does at night, when he spends all night in the office on the computer on facebook, you know its not right.
While my XH was supposed to be working on our marriage, he was texting her all day every day, therefore his head was full of her, it wasnt full of me and our then 3yo DD. He even emailed her right through our family holiday, texted her throughout family days out, family events, he could not live without the contact.
My XH kept his phone on him at all times, he slept with it beside the bed. He wouldnt let me near it. He deleted all texts and emails so that I couldnt read them, it was only by chance that I found the things that I did. he took it into the toilet with him, to the utility room, if he popped to the shop, he took it every where that he went.
I divorced him in November 2012 because he was adamant that it was over, that he would not come back. and he was still texting that woman. A woman who is married to his best friend and who married her first husband while cheating on him with the man who would become her second.
People always recommend this link
www.shirleyglass.com/quizfriendship.php
I am really sorry for you, but your H has crossed the line, he IS cheating on you and you need to put a stop to it. you need to see if you can find any evidence and then the best thing that you could do is tell him that it is not acceptable and ask him to leave while you both consider your options.
But you do need to prepare yourself, that it may be more than just emotional. But don't let yourself be taken for a fool like I was.
you are his wife, you are supposed to be his best friend.