Over the course of about a year or so I've slowly been losing interest in everything that I used to find interesting to me.
As long as I had the same problem a few years ago, I can state that it was connected with the routine I lived in. You need to get out of your comfort zone, discover new activities, meet new people, see other places, and even find new paths home from your work. Don't let yourself stop trying to find what you love to do, anything that brings you joy and relaxation. You won't lose interest in things that make you happy.