I need help i really really suck at interviews, im sure that they see that i am not confident enough,?

i stumble over my answers, im not quick on responding, and the most difficult questions to me seems like the ones about me, which seems weird how do i not know myself it really makes me mad when i mess up on interviews i just want to cry when i leave im so hard on myself and i dont know what to do it hurts so bad, because i really want the job and i know i messed it up. I have problems with the questions that say 1. tell me about yourself? ( i do not know what they want to hear), 2. Why do you want the job? ( I never know what to say) 3.why should we hire you? ( I never know what to say for this one). This is what people say about me and what i know i am Organized, outspoken, persistant, honest, and dependable. I sometimes feel maybe im not confident enough because i feel i dont speak proper english I graduated from high school and everything its just the school i went to if you spoke improper english they did not correct you and so now im all messed up.