Struggling with Identity and Memory Issues

I’m not in any way a professional, but if I had to guess that sounds more like a dissociative disorder than a personality disorder. What you described sounds a lot like OSDD (otherwise specified dissociative disorder), where it’s possible to have multiple personalities, but not full amnesia. That would explain the problems with your memory, even if there aren’t complete gaps. I’m not sure if this is what you meant by “switch,” but maybe looking into dissociative disorders could bring you some more clarity. (Side note: MPD—multiple personality disorder—is not a personality disorder, just the old name for DID—dissociative identity disorder)