I have been married for nearly 18 years, 2 DC, lovely home, lifestyle, good and kind husband (!) etc etc. But he has a female friend he has known for much longer than me, on and off over many years, periods of not being in touch and I think they have had a physical relationship at some point in the distant past (not completely sure). In the past two years his contact with her has become more frequent, at least every other day, if not daily and he won't let me see the messages they send to each other. Occasionally he will lock the bathroom door and I can hear talking from him but nothing in reply. At what point is this friendship more than that? Is it already?