It really sounds like you need some help right away. I'm sorry to hear that things have gotten so bad for you. Are you open to seeing a therapist? Sometimes having someone who's not intimately involved in your life to talk to about what's going on can be much more helpful than talking to family and friends who probably are a lot more invested in your decisions. Drinking alcohol and using drugs might temporarily numb the emotional pain you feel, but will ultimately make things worse for you- alcohol is a depressant, so that will actually lead you to feel more depressed.
There are lots of people who struggle with the desire for more and/or questions about what life means and what makes it important. These are upsetting questions but they are not worth dying over, as, with some help, you can sort out answers for yourself and end up feeling much happier in your life and relationships.
It is also very important that you reach out to people at times that you're thinking about hurting yourself. You can always call the National Suicide Prevention Lifeline at 800-273-TALK for 24-hour support. It seems very important though that you additionally find a psychologist who you can work with at least once a week for help.