20 year marriage

I've been with my wife now for 20 years. She has been traveling for 15 of them, at least 2 to 3 times a month. I have always felt like she was up to something extramarital. She has always replied with I'm not cheating, it's all in your head, you're crazy....etc. This has been going on throughout the last 4 to 5 years. Up until recently, I couldn't prove anything I was feeling to be true. I found some text messages between her and her boss on our IPad. They were pretty clear to me, but could have possibly been read and interpreted another way. When I confronted her with them her response was we were just joking....
I knew that wasn't the truth in my gut at the time.

Since then I have overheard some conversations between her and her boss that had nothing to do with work. They were more like something that you would say to somone you were dating. I started paying more attention after that. Very close attention to everything. I finally got her to admit that there was something going on between them. She swears to my face that she has ended all communications with him. I have heard her still talking to him and making plans along with other crap. I am having a real hard time believing anything that she says now because after all that I have heard them saying to one another

We've started couples counseling and she is using the counselor to make what she admitted to doing is somehow my fault. I made her do what she did with her boss. I know that sometimes well more than sometimes I can be a prick. However, I never cheated on her. I never did anything the could have justified any action like this.

I still love her but I don't think that a will ever be able to trust her again. Has anyone else going through this type of situation before? If so any advise would be helpful. Thanks