Hello. I'm really sorry about your situation and I hope your suffering stop soon. Today, thanks for a topic here about the book "Final Exit : The Practicalities of Self-Deliverance and Assisted Suicide for the Dying", I found the work from his author Dereck Humphry and his society "Hemlock Society USA). If you live in the USA, maybe you can have some help from them, just for having the choice before cbt with SN.
The book mentions the bag method and I'm considering it. The author says that It's 100% efective and painless, with some medicines (like diazepam) of course. I hope this could help you a bit. Good luck friend