OP, I've had periods of situational depression in the past, including attempting suicide, and you are implying a form of suicide in saying you would not seek medical help if you became ill. I've also previously self-harmed, which you are doing in a way by not eating.
I have been okay for over ten years now. There is hope, you can come through depression. I know mine was situational rather than clinical but it was still very bleak and I know others with clinical depression who also say that there are peaks and troughs, good times and bad times, it is not all bad all the time.
Try not to think too far ahead. We can none of us predict the future, not even the scientists. On the days when looking to next week was too much, I told myself I'd hang on until the next day. On the days when the next day was too far away, I'd hang on until the next hour. I was taught that if I felt the urge to hurt myself, tell myself I'd do it tomorrow, or I'd do it later, and just push it a bit further down the track. Because the really bleak feelings don't last forever.
If you won't see your GP, would you try speaking to the Samaritans or phoning another helpline? I have found them helpful at times of crisis.