Sounds like a very difficult time, I'm sure it can't be easy for you or your family to deal with the disease of addiction. Addiction is an insidious disease, affecting not only the user but everyone who cares about him/her.
I'd imagine your dad is struggling to deal with this emotionally just as you are.
It's times like these when we really need to count our blessings and learn from our mistakes. It really sounds like you want to be free from your disease, but the only way to do that is to get substance use under control... a lot of the time that means abstinence. Opioid replacement therapy may be beneficial in helping you step down from heavy heroin use, but I'm not really sure if there is a replacement therapy for amphetamines.
You may never fully recover from some of the damage done, but you will benefit greatly from stopping the damage from occurring, and you will be able to recover a lot of your health back. Things may never be perfect, but they definitely can improve if you take action to change your behavior. It sounds like you would benefit greatly from substance use counseling. An inpatient treatment center and detox can help you get past the acute withdrawals and overcome the emotional turmoil that will follow.
In the end, no one gets better without addressing the things that are driving them further into addictive use. Things may be bad, but they can always get better- or worse.. depending on which way you decide to go. Don't wait until everyone has given up on you... Your family may not know what to do to help you, but I doubt they want to hurt you.. I know I caused my family a lot of pain with my drug use. I felt so isolated and alone when I was using, feeling like no one understood me and that my family didn't care. Truth is it was really hard for them to watch me suffer and they didn't know how to help. They may not understand you, but if they haven't abandoned you then they definitely care. Going to rehab was actually a very positive experience for me, it was really difficult at first but in the long run it brought me closer to my family. Being able to admit and talk about my problem was very freeing.
My mom tells me all the time how happy she is I'm not using anymore.. She never really confronted me while I was using, but it's clear now that I was tearing her apart by destroying myself with my drug use.