I'm so sorry. It's so clear how much pain and distress you are in. I wonder if assisted suicide would be worth you enquiring about. It's clear that you are suffering terribly. Do you have any doctors or care givers that you could talk to, or contact?
Unfortunately- with methods- it feels like it has to be something you would need to make a decision on and acquire yourself. It's illegal I think in many countries to assist a suicide.
I understand it must be awful to not be able to secure a method for yourself- it does sound as if you would be unable to do this. So- I really think that speaking to your healthcare providers might be your best option. I really hope they are compassionate.