You mention that when someone you care about leaves you, you don’t feel sad. It’s possible that in your early years of life you experienced abandonment, rejection, or loss of some kind, but you conditioned yourself to not react to those events, by forcing yourself to stay numb. This could be a defense mechanism, or your way of protecting yourself emotionally. It’s possible that as a young child you were discouraged from expressing emotions, so you push them deep down, where they become sub-conscious. Another possibility is that you are genetically wired to not react emotionally to loss. Maybe one of your parents is like that, and you inherited the gene? It would be interesting to know what your other emotions are like. We all have an internal emotional regulation system, which develops uniquely based on genetics, early attachment, life experiences, and inherent personality. A combination of all these, affect how we respond emotionally. While your emotional response to loss doesn’t seem to be “normal”, it has probably developed that way for good reason, and somehow keeps you safe.