I'm out of town right now, and my husband has been regailing me with stories of taking this girl from school all over the place. What should I think?

I’ve been out of town for a few weeks, and my husband who is usually a quiet ‘gamer’ kind of person and goes to school then to his game store, has suddenly started to do things with a classmate. I know her, and he tells me about it, but it’s strange things that he would never ask me to do, like drive 3 hours 1 way to go SALSA dancing! I would love to do that, but he would laugh at the idea if I brought it up; the last time they went they got home at 6am. He also said he was at her house and now he knows what a ‘real house’ should look like… (We are both artists, and don’t pay alot of attention to the details of the domestic chores.) I was furious, and finally let him know, and he can’t understand why I’m upset. Does anyone have any insight into this??