All I can think about is suicide how can I stop this?

Suicide has infected my thoughts. I have an obsession with the idea of dying young and how romantic it would be to die a star crossed lover. But I know it wouldn't be. I have so many flaws I just deserve to die. It's my automatic solution for everything. Say something stupid kill yourself. Fail A math quiz kill yourself. I honestly feel worthless. Nothing I do is worthwhile people won't remember the things I do because they are all stupid. I'm impulsive and moody and my family hates me. All I do is debate and argue. How can I stop myself from being obsessed with killing myself? Its getting really serious because I am actualy considering suicide. Don't try to pull that "Suicide is a permenant solution to a temporary problem" bullshit on me because I will always be this way! People don't change!