So when were you diagnosed with PTSD? Have you worked with a therapist for the PTSD?

If you suffered from abuse at an early age it is possible that you unknowingly developed ways to distance yourself from others to self protect. Your ability to form attachments for others may have been disrupted if you suffered enough abuse as well.

It is something you should explore with a psychologist. One of the symptoms of PTSD is "avoiding" reminders of trauma/traumas so
if someone who was supposed to "care and love you" hurt you, it may not
be so much that you don't have empathy as much as you avoid it.