There is no pain free way. Every method has the possibility of failure, and some of the most “pain free” ways have some of the most ugly drawbacks if it doesn’t work. Like a lot of people think taking opioid pills is going to be the kindest, but if you don’t die you can wind up very crippled.
The best way to sort the pain is to go to the emergency room. Tell them you’re suicidal. They’ll probably put you on a ward. It’ll be a week or so. You’ll calm down. They’ll adjust your meds. You’ll find that one nurse who listens to you and you can open up with. And you won’t die.