Hi, I might be wrong here, I have episodes of hearing voices, I have been diagnosed with a few different things including hypermania bipolar and BPD. I asked the Dr about voices and schizophrenia, he told me that as well as other factors where the voices appear to come from plays a big part in diagnoses. If you hear voices in your head that is probably BPD, if they are external voices that could suggest schizophrenia. There are other elements to take into account too, self harm is usually accosiated with BPD but not exclusively, as paranoia is to schizophrenia. My voices are external but it's my belief that the voices are magical and friendly has lead the Dr to think they are related to the hypermania, also the fact they are not a constant and seem to be episode related. It's so confusing I have just confused myself.
I think in short what I am saying is that the cross over of symptoms from one illness to the next is what makes mental health so hard to diagnose and why so many people go undiagnosed and untreated for so long.
Good luck with your diagnoses, BPD is an awful illness but there is there so much you can do to help yourself if you really want to.
Oh and well done on not self harming