Your dad isn't leaving you. He'll always be watching over you.
Just stay strong. You're still here and that's a good sign. There is always hope and things will get better even though it doesn't seem that way yet. I used to think about suicide quite often when I was depressed and felt like nothing would ever get better but when I least expected it things went right.
It's also about changing your attitude. Try a little optimism. It is tough to be optimistic when you're feeling that bad but it can be done and I think you're strong enough to do it.
Just hang in there dear.
