Dear Abby, I've never written to you before, but I really need your advice on what could be a crucial decision. I've suspected for some time now that my wife has been cheating on me. It's the usual signs... phone rings but if I answer, the caller hangs up. My wife has been going out with the girls a lot recently - although when I ask their names she always says, ""Just some friends from work, you don't know them."" I always stay awake to look out for her taxi coming home, but she always walks do…