While on vacation with family I found a text from a female co-worker asking why my husband was not at work. He replied that he was on vacation with his grandkids and daughter ( no mention of me ) . She replied what are you doing . He replies sitting by the pool drinking a beer on a lawn chair wishing it were you. He tells her he wishes he were on vacation with her . She asks where and he says anywhere,anytime. I confronted him and told him I was in shock after 40 years of marriage that he would do this. He says it was joking around. It means nothing . I have had a headache and can not eat , it has been 4 days and I still can't get this out of my mind. We talked and every question I asked him his answer is I don't know or I must have missed typed it or you took it the wrong way. Am I crazy ? I am broken hearted .

No, you're not crazy.
BUT here's the deal: either it really is joking around and is typical office shenanigans to lighten the dreary day, apparently very common, or it isn't. We don't know (at least I don't). But I do wonder why someone who is close enough to him to banter this way doesn't know he's MARRIED and living with his wife? If not - why not? I would grill him on when she started working there, how often they see each other, how old she is, her marital or relationship status, how she might think he's divorced or separated, and any other checklist item you can come up with. Do it calmly, like it's a job interview. Which it is - he's being interviewed for the job of HUSBAND. Tell him that.