Dear ridiredhood,
feeling suicidal is serious and you need to act. You are MUCH more important than any finals. Your health and wellbeing (both in body and mind) need to come first.
Breath. Is there a suicide hotline in your country you can call? It can help to talk to someone directly. Look up the number and call them right now.

Also feel free to post here anytime. How do you know that you will fail? Is it a fact or is it your fear talking?