I dont trust the public mental health system either, I also suffered PTSD from being in their "care".

Is there any way you could get into the private system? Still some dodgy stuff going on from time to time but it is much much nicer than state or public facilities, and a better quality of doctors (at least in my country). A private clinic stay might help you get to the bottom of what is causing these dramatic emotional swings and the doctors will be able to observe you to give a correct diagnosis. I realise that may be out of your price range, but just a suggestion.

You do need to be honest with how you are feeling to get any type of help. It can be hard, and if you are really keen to stay out of hospital just offer a "guarantee" (signed or otherwise) that you will stay safe between visits. They may not force hospitalisation on you then. Usually works for my pdocs.