Lying about ex wife

I just found out my husband has been texting and calling his ex wife almost daily for at least the past 18 months. A lot of the calls were 30 minutes long, some even longer and there were days when they texted back and forth all day long. He deleted the logs of all these calls and texts with her. I have asked him before if he has talked to her and he always said no, he even saved a text from her that i knew about and would show me on his phone that it was the last communication he had with her. I found out because he gave me access to his cell phone bills after I caught him lying about her...they have an adult child together so I expect some communication, but this seems like too much and I am really hurt by the deception. He acts like he did nothing wrong. Am I freaking out about nothing or does this sound concerning to anyone else?