I might not be able to p 8th grade, Please pep-talk? ?

Im scared that I may not be graduating 8th grade this year (2009) due to one F, Im already getting an F, its due to the quizs and I am a really bad test taker, Mr.V, (Teacher who teachs the cl im failing; Us History.) his cl is really hard, Im in Special Eduation also, so its really over the top of me head all of this! and today our Vice came into our homerooms today and said that "If we fail one cl, we are not able to graduate this year, and we have to do 8th grade over again." I didnt get any sleep last night, I was crying my eyes out worrying, and I hate it when they say "Its really hard to get it back up" Currently my grade is a (54% ave in this cl,F) so what can I do not to worry, I feel like killing myslef sometimes, and I have tought about doing it sometimes, Im so scared, Please from the bottom of your heart! Help me ? Talk to me please?