Hi there ... Sorry to hear that you're suffering and are in emotional pain.
I've taken up hitting myself recently and I haven't really figured out why I do it (apart from being punished feels good and that I am somehow 'waking myself up'). I've switched from hitting my face to now slapping my hands as I thought I might injure myself by detaching the retina of my eye.
My diagnosis is major depression with psychotic features, and I also have anxiety and some OCD.
I have also gone periods where I am not able to keep up my hygiene. In fact, I now have periodontal disease because I couldn't brush my teeth everyday. I'm really sad about that.
I, too, seem quite functional at least to the outside world and I tend to under report, as well.
It is difficult to find a good therapist, I think.
I have also thought of euthanasia.
The reason I am writing, even though I do not have the solution at this time, is to let you know that you are not alone.
Maybe if we really calm ourselves enough to think, then we will find the answer. And I say that because I'm giving up hope that I will find a good therapist who will help me find the answers. I'm going to have to find the answers myself, I think.