Honest opinions wanted please. 30f 35m

Hello, So my 30f husband of 9 years 35m had been secretly messaging an ex. Not just messaging actually, there has been video calls as well. It's been going on for 8 months. In some of the messages he calls her beautiful and there's jokes about sending nudes pictures. No pictures have been sent that I can see. At one point he asks her for something nice. But then there doesn't seem to be a response. It is possible that messages have been deleted. I found them accidentally when the chat popped up on the computer as I was doing work. I was in total shock as I wasn't expecting it at all. She even jokes about how mad I'd be if I found out. He claims that the conversations and video calls were just friendly and they were just catching up though he admits that they appear flirty in places. My question is, am I stupid for trying to move past this? I feel like there was more to it than I'm being told. They can't have met up or anything as she lives a long way away from us. Really wanting honest opinions please. Does it sound like there was more to it? I thought we were happy but then this has happened and it's totally thrown me and made me question everything.