Well, it is the stuff of tv shows for someone to be 6 and a half months pregnant and not know it. It's really unlikely. She'd likely be showing and have other signs. It is probably more likely to go unnoticed in a heavy woman than a petite woman. She can do one of two things though which include taking a home pregnancy test right now or going to see her doctor and doing a test at the doctors office. Once she has done that, it is time to get to work on her mental health. It's really not fair to you to be constantly up and down based on her emotional state. She has a responsibility to work on it. I am very glad she is in therapy and perhaps she needs to start or change her medication. Psychosomatic illness or things like stomach aches due to anxiety are common but the key is to address the anxiety as fully as she can. Is she working with a psychiatrist? I'm sure this is hard on you both.