Urge for no reason

Ever since I was fourteen or fifteen, I have had many, many fleeting periods of suicidal thoughts. They come often at times of stress. I will take a walk at night and consider throwing myself under the wheels of the passing truck. I am a rock climber, and I have tied a noose out of climbing rope and put it around my neck five times, just sitting alone. Last year I lived on the eleventh floor of my building, and considered pitching myself through the screen and out the window. I have gotten drunk and pulled a knife across my wrists, imagining what it would feel like. I have been tempted to take all of my Adderall at once.  I recently found a note I wrote to myself my senior year of high school. I describe the same feeling I have these days, but also that “I am not a suicidal person”. Like I’m trying to convince myself of it. Through my whole life, I have had a wonderful experience. My parents care a ton, I have a good social life, I have a girlfriend of more than a year, I am doing well in college classes, I am working part time, I feel happy most of the time… My life is awesome. I am grateful for all of it. So why am I fixated on suicide? I used to tell people, but I haven’t for a long time because it is embarrassing to appear so pathetic. I don’t self mutilate, do any recreational drugs, and engage in sexual activity responsibly.  Does anyone else have a great life, and nothing they would want to kill themselves over, but still get huge urges?