Is all of this enough of a wake up call to get help with your drug and alcohol problems?

Suicide will only make your former GF carry enormous guilt for the rest of her life. Do you really want to hurt her more?

Of course you don't. Please go and get some help. Right Now. You can turn this thing around. Maybe not with the GF, you did treat her pretty shabbily, but fix you, let her know you are on that path and that you are deeply sorry.
Let her know that you recognize you have a problem and she was the best thing in your life and you will never deserve such a lovely girl as she. Then get Real Help and make a new life without the substances. She may be watching and remain your friend. You never know, she may get past this with you, but get going. Show her & yourself you are strong enough to be better.
You can do this. It will likely be hard, but most hard things in life are totally worth it. Best to you and keep posting. We here are on your side...