Please help me figure this out!!

My boyfriend recently started texting and calling his ex wife. He has been acting strange... he takes his phone everywhere he goes...deletes all texts to/from her and even changed her name to a guys name. The only reason I know he changed her name is because I saw a strange text and the name and reply did not make sense. I check his usage and I saw that it was from her. When I asked him about it, he says he deletes the texts and changed her name so I would not flip out if I see a text from her.
I went as far as asking him to call her in front of me or text her and to show me her response. This way there would be no doubt that he is being truthful. He got very upset and said that he did not want to get her involved.

In the end, he did text her BUT did not show me the text he sent to her or the first response that he got from her. The only ones I saw were the couple after....and those said there was nothing going on between them..
He swears he has nothing to hide and there isn't anything going on. He is very upset with me because I do not trust him and that I have become obsessed with checking his usage.
Am I crazy?? Should I call her? What do I do?
Thank you!