I'm no expert on the subject but, as some others above have already mentioned and being a sufferer of it myself, I too might venture to guess that depression is at play here. Maybe now would be a good time to see your family doctor and/or a therapist in hopes of finding an answer (along with, hopefully, a solution). It's common to lack enjoyment in certain things from time-to-time but not "the norm" to lack enjoyment in anything and everything on a regular basis. Sorry to hear you are feeling this way, I wish I could offer more than just my few words.

All the best to you!