Here is some advice:

If you think you have a problem don't sit back and wait, take action.  The longer you wait the more pain you will feel.  Here are a few things you can do to take action.

1. Talk to someone you trust. for me it was my closest friend, and my boyfriend.  Trust me, i thought that they would think i was crazy.  i found out that my best friend was exactly the same way, and they told me about them whilst i told them about me.  my boyfriend he had been that way and he told me that i need to talk to someone other than him.
2. Talk to a counselor or an adult that you know and feel safe with.  For me that was really hard.  i was terrified to sit in room alone with an adult, and i still am but not as much.  Tell them and if they are truely there to help they will.  i mean its hard to think that they wil but once you tell them they will ahve so much to say to helop you and relate it to their life which is much more complicated BELIEVE ME!!!!  if that isn't your style or you are just too scared do the next step first.
3. go to the library and read some books on suicide, self-infliction.  You'll find out that most of it is caused by depresion, PTSD, or other mental (not necassarily crazy or insane) problems.  right now i am at that stage.  i think i might have depression or PTSD or bio polar disorder.  i need to go and research the symptoms.  There are many books that you can find and by the time you get through them all if you haven't completed number two you'll relive that it is better to talk than to keep it all to yourself.  after you tell someone you feel the pressure being released and you relive much more about youself.
4. this is one of the biggest steps you can take...TALK TO YOUR PARENTS.   i haven't gotten here and i don't know if i ever will but i do know one thing...they will understand.  if you think that they won't just think...." I thought that that other adult wouldn't understand but hey they did maybe it will be the same this time as well."  just look on the upside, either they get upset and try to help you or they get someone that can help you. 
5. talk to a complete stranger.  it is really hard to talk to a person that you know personally but hey if you can't talk to them talk to someone that had no clue who you are personally or the way that your life works.  it's nopt like you walk up to some random person on the street and say, " oh yea ummm...by the way my life goes......"   NOOOOO!!!!  you go  to a doctor that can actually get on on some medication or something that will help you get over the problem....because if talking didn't help the only thing that will is medication.  

remember things could always be worse.  SOMEONE ALWAYS LOVES YOU!!!!!

ok this is a start.  first follow the simple steps (ha ha) that are above.  yea i know that it is hard to do, i felt/ feel the same way but it helped my best friend why not you or me.  ok then after you have done that you need to spend some alone time with yourself.  you need to meditate or sit there thinking about the reasons why you think you should die and find counters for that.   trust me the good things about you alway out weigh the bad.  i ahd my boyfriend break up with me and friends turn against me then i realized that there are other friends that are there for me and that would never hurt me. i also realized that there is a right guy other there for me that loves me with all his heart...i just have to find him.  ok then you have to "become friends with the knives/ medication" that you are using or are planning to use.  Tell yourself that you are not going to use it.  here's an idea..... put it in a box in your room that is see through....LOCK IT!!!!! MAKE SURE THAT THE KEY IS NOT ABLE TO BE FOUND!!! (give it to your friend or a loved on that will not let you have it back ....EVER!!!)   ok then just stare at the knife, the more you start to think about it the more you won't want to do it.