My husband of 15 years seems to have lost interest in our marriage, and I suspect he is having an affair. My mother thinks I might be depressed and that I pushed him away by being emotionally and physically unavailable.
The simple answer is that you should listen to your mother before you take any further steps. That, however, is not the same thing as telling you to stay on or leave the marriage, it is simply that in many (not all) instances, mothers offer their advice to their children from a position of both wisdom and love.