I'm A 38 Year Old Female. I've Used Drugs Intravenously

I'm a 38 year old female. I've used drugs intravenously for 6 years. I've recently been injecting meth. I've only missed once. I currently have a wrist that I can't move, a knee swollen tovtqice it's size and now my shoulder is killing me. I have picked places on my back and I believe they are infected. Could this be infection or from the meth itself?