I don't know if I can say anything that can help but I can say that I can relate to your depression and wish to die.
I have made one suicide attempt and thought of it many, many times. Like you I have wished to die of disease to spare me the pain of living. Earlier this year I was called back for a repeat xray when something was suspicious on my mammogram. I hoped it would be cancer so I could die from a respectful cause rather than suicide.
Earlier this year I told my son that someday I would likely kill myself but I didn't know when. Next year, ten years, twenty years, who knows? I told him I had a plan but didn't tell him what. He surprised me when he said I would die in the barn, right? He was exactly right. The barn with my horse has always been my safe place and a place of peace to live and I think to die.
I don't know if I am making things better or worse by discussing my thoughts. I don't intend to make things worse but want you to know you are not alone.
The best thing I can offer is that depression can get better. I have actually had a good day today because I spent time with my son and with my horse.
If you are not on medication you should be (IMO).
Hold onto what it is that you are living for. For me it has been to raise my son. I know my son needs me now and that keeps me alive. Your child needs you too. Look at your child's face and focus on the beauty. If you have only one reason to stay alive it is to raise that child.
Sending you enormous hugs in your moments of pain.