We are so glad that you reached out. Having suicidal thoughts is a very serious concern. You mentioned that you think you might hurt yourself soon. Please know that we care about you and want to make sure you are safe. Can you email back or call in so that we know you are OK? We do believe you when you say that you are tired of life, and that you feel like no one cares. It sounds like both your brother and sister have chosen some unhealthy paths themselves, but there is a lot of hope for you -- why?
Because you can already see that drugs and alcohol are not healthy ways to live. You can already see that getting into unhealthy relationships is only going to be problematic. You're a smart girl.
Sometimes when others are caught up in their own problems, they don't see that it effects others in their family. You mentioned that you love horses, sports, and music. Those are all great activities and hobbies to have. We sure hope you keep yourself involved in them. It is so very important to be sure you keep things in your life that are important and enjoyable for yourself. Sometimes these activities can even be great distractions for you when you are going through troubling times.
Yes, it would be ideal if you could talk to your parents about how you are feeling. In fact, after their initial reaction, they probably would be worried about you and want to get you help. If you do no think you can talk to them, consider talking to your counselor at school. You don't have to go through this alone.
We don't want you to continue to feel alone because you are used to it, because there is help out there. So, please keep safe, and write back to let us know how you are doing.