Help! Am I crazy??

Really need to know if I'm being crazy and overreacting or if I'm in my right mind...
So there is this girl that my husband works with and he has apparently become good friends with her. She gave him donuts at work last week and he always comes home and talks about her. (She's also married.) He also wants us to go out with her, her husband, and another girl to celebrate the two girls' birthdays at a bar. That's fine and all, but whenever I want to do something with him he doesn't feel like it and would rather play a video game. Also, there is this festival this weekend that I've been talking about us going to all week. He has been not interested in going at all. Then today he tells me that this same girl from work is going and she said the weather will be great, so now he's all excited about going. ??? 
I hate feeling jealous! Am I driving myself crazy for no reason? Or does this seem weird to any of you? Also, I don't even know if I should bring it up to my husband. I know he will just get mad and say I'm overreacting. So if I did bring it up I don't know what to even say... 
Help please!!!