Depression Support Group
Depression is a real and debilitating condition that is often misunderstood by family and friends. Its meaning can range from a prolonged period of sadness to an actual mental illness with specific symptoms. Find and share experiences with others who are going through the same struggles.
You must confide in your parents as soon as possible, I reckon. You may not want to hurt them but can you imagine the pain they would feel if you killed yourself and never told them anything - it would be far worse.
I see from your profile that you're only 18. You have your whole life ahead of you. If there is a God it surely won't be pain for the rest of your life; or if it is there'll be a way to cope with it, manage it, so that you'll still have good quality of life.
The last doctor you saw...I take it you've seen a few; if not, definitely get a 2nd or 3rd opinion.
Try alternative medicine or chinese medicine. Medicinal marijuana - would that help?
A book on how to live with chronic pain and illness:
https://www.amazon.com/Live-Well-Chronic-Pain-Illness/dp/1614292485
I have a friend who's suffered from IBS and other things his whole life too - he hasn't given up yet though it's taking its toll on him.
Lastly, there is the possibility of a miraculous healing. It has happened to some people who go to places like Lourdes or Medugorje. One woman who, I think, had cancer went to Medugorje as her last hope. She returned home but a few months (or was it a month) later died from her illness but she or her mother (who had gone with her overseas) said that though she wasn't physically healed, the spiritual healing that did take place was more important. God bless you always! : )