Thibault, I feel for you. As an expat I recognize many of the symptoms. I’m probably a bit older than you so most of my family have passed on, although I still have friends in Europe. It sounds to me like you are a bit down in the dumps. I usually long for my home when that happens, and then it passes as something nice happens. Your work sounds like another issue. If it is killing you then deal with that first. On your next trip to France, tell your friends and family how you feel; perhaps they are better able to offer support.