This is really tough.
For one, meth is a very dangerous drug that absolutely will rob you of your health and life after a while. Meth is a stimulant as I'm sure you know, so anxiety is an understandable expected effect, HOWEVER, injecting meth will put you at a significant risk for various serious medical emergencies...like cardiac events, blood clots, stroke, etc. Please read the following:
http://www.thegooddrugsguide.com/methamphetamine/dangers.htm
I'm not trying to scare you, this is just factual information. I strongly urge you to seek intensive addiction treatment to try to get clean and stay clean. Your health really does depend on it. As for symptoms like chest pain, I would get that checked out medically. While you do, you can ask for help with your addiction.
We have a wonderful addiction community here...I encourage you to reach out there as well:
http://www.medhelp.org/forums/show/77?camp=msc
I wish you the very best, please update us when you can!