Do I have a right to be worried?

My husband of 6 years has been texting a female friend (she has a boyfriend) our children are friends that's how we all know eachother. He has been very secretive with he's phone lately so I decided to have a peak when he was sleeping to which I found quite a few exchanges of messages on whatsapp, they are casual messages asking how eachother are and what they have been up to etc. There was one message that did concern me and that was him telling her that he is always in my bad books and that I have lots of washing and chores for him to do. I don't know why he would talk to her about that kind of stuff as they aren't that close of friends. She has seemed to be initiating the messages but he always replys and sometimes there has been lots of messages. It's not every day but I still feel quite weary of this she is younger and attractive too. Any advice will be appreciated ty
Do I have a right to be worried?
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