I'm so so sorry you feel so lost. I really hope you find some support, you need and deserve it. SI is very addictive, it is possible to stop, but you need support. Is there a crisis line or something you can phone when you feel that way (like the British Samaritans)? They will talk or listen, whatever you need until the urge reduces, some organisations will phone you back if the phone bill is a problem.
The volunteers do it because they care and you are just the sort of person they are there for.
You are a human being and therefore precious. You deserve the help.