KJ:
With HIV and Hep C, it is extremely important that you take care of yourself. You have a tough combination of issues there.
If you are using needles, stop sharing. Get your own, new, clean needle and learn to sterilize it safely, or find a needle exchange program. You have a much higher than normal risk of contracting anything to which you are exposed. I'm sure your conscience will not deal well with learning that you gave someone else HIV and Hep C.
Willpower alone is not going to stop your speed habit. I commend you for trying to stop. Keep at it, but find some help. Speed is a risk to your health. In addition to the cardiac and other health problems it can cause, it will cause you to take even more risks, which increases your chance of compromising your health and well-being and being harmful to your friends and family. Either you still find something rewarding in taking speed or your are just addicted. Maybe you just started on a whim, or maybe there is a trigger, driving you toward the habit. Everyone wants to feel good. Perhaps you are impulsive by nature, or you feel bad. Maybe you are trying to fill a need you don't understand with something that will not help in the long run. An addiction counselor or psychiatrist can help you understand what is going on inside yourself and help you to overcome the habits that are doing harm to you. I encourage you to seek help. If your doctor does not have a recommendation for an appropriate professional, seek one out yourself.
Take care.