What should I do? I feel myself becoming dependent on drinking, doing drugs and smoking and I can't stop.
Why do you think you are dependent on it?
it might kill me, they are bad for my health.
It's good that you're accepting that drugs and alcohol are ruining your life. You definitely should seek professional help or go to rehab.
I do need more support for my addiction.
It's good to realize that you need more help and support for an addiction. Talking to a therapist or going to AA is most beneficial.