Is this close to an office affair?

I was trying to reach my H on his cell phone but he did not pick up and then I heard this message from his female co-worker: hi...I just had my surgery done....I was so scared but you are the first one I want to talk to about my situation.....I am feeling good now...my dad is taking care of me....I just wanted to call to tell you this.....well, I will see you next week in the office......... (later I found she called him with her ID blocked.

I vaguely know that she is a new employee, young & married but have no children. Even before this, I sensed that my H has been close to her although he does not talk about her too much. She would call him every time he did not go to work....sounds like she was trying to tell him what to do the next day when he gets back to work. Another time she called in on HOlloween to ask H how everything was going with my kids to go out trick and treat....

I definitely think they are too close, aren't they? I don't think they are that close yet as to get into bed.....but closer. Am I too insure? I know my H has the pull in this. but when I was mad about this(I was just not able to control myself), he was so sweet and nice and saying that was completely co-worker relationship.........

What drives me nuts in this situation is that he says I was in bad, desperate mood in reacting that way. I just wanted to hear the readers here if I am unreasonable to react that way? I am not sad or anything......maybe just a little angry. But I have to clear my confused mind here.......that will help me to how look at this man and decide about my life in the future.