Am I over reacting?

So my husband has a friend from work who is a girl. A single girl. I was not home and he decided to go to her house at 1AM to hang out. He told me about it but I was still soooo upset. A week later I stay at a friends house again only to find out she went to my apt at 1AM!!! My husband does not see why I am so upset and hurt by this. He thinks since he told me that's it's ok. I believe him when he says they are just friends and nothing happened but I'm still so upset. Idk how to get over this. Idk if I can. Any advise???