Shouldn't my husband tell the girls he soes business with that he is married?

The girls are overseas & they do business thru the internet. I saw some instant messageing that I thougt was inappropriate. One girl in particular. THey wrote how much they missed talkeing when they couldn't get on line & think about each other all the time. I think This explains his later hours sometimes & total lack of interest in me. When my husband was sick she asked if he had someone to help him which he didin't answer. I help with his elderly mother also and on her b'day he told her he & some "friends" to her to lunch. I found a saved one that seemed overtly sexual. When I asked him he acted as if he did/nt remember it but finally said maybe he crossed a boundary. He refused to tell her or the others (which were beginning to go in the same direction) that he is married, because he says he has to do business with them. He has never apoligized or anything. I have been very hurt and feel as if none of the thngs I do for him matter.Its as if I don't exist.. We've been married only a few yrs. He was single all his life and is late 50's now.
What else should I do & am I over reacting?houlI'