I've never seen this thread before and I have to say that sometimes, especially in the past for over a year, I had this feeling. Or lack thereof. I felt nothing but pure emptiness. I don't know what caused it, but I eventually got over it somewhat. I still don't feel too many emotions. But I feel some and they feel good to me.
I don't think what you are experiencing is enlightenment, because enlightenment does come with the constant euphoria package I believe. But that's not from personal experience, just from what I've read. I'd say you've lost a part of yourself, and it is a pretty important part. Your emotions are very crucial to making any decisions. The empty feeling and apathy could very well be a different form of depression.
I would go to get some kind of psychoanalizing done. Some kind of mental health assessment. Something to bring light to what you are going through. Another opinion, and one of a professional. At least then you'll have some idea of what is going on. Otherwise, you're just kind of getting opinions of people who are not certified in any way to tell you what is wrong. They can try, and some of them may be right, but they are not trained to make any diagnosis. Get help...seriously.