I think I first thought about it when I was in elementary school. I can't quite remember, but probably between 7 and 9 was when I started fantasizing. Of course, at that age, you don't even really have a fully realized personality, so it questionable what it means to be suicidal at that age. But I started seriously wanting to starting in middle school and it's gone up and down since then, with the past couple months being the worst (best?) it's ever been. Usually in the past it was a more abstract misery and depression, but this time I have been thinking more clearly. Although it was set off by a traumatic, extremely emotional event, it made me realize a lot of things about myself and the world. The key thing being that the world really fucking sucks and the amount of effort that is required for me to keep battling my everything isn't exactly worth it considering what the future looks like.
So about 20 years.
My story is similar to yours... without the traumatic event you (sadly) went through.
Pressure at school (school bullies, teachers, parents), at college (roommate bullies, parents), at home (relative bullies, parents), at work (workplace bullies, parents). I'd always shrug it off as an obstacle that had to be defeated... then on 2022, I realized all of my efforts were pointless: Unemployed, entrepreneurial failure, candidate for developing dementia, unhappy most of my life, somebody's bitch... the list goes on.
If nothing can turn out right for me, at least, I hope my attempt to CTB won't be another failure.
Quick, maybe not easy, and painless.
We'll see how it turns out.