By any chance are you on a form of birth control ?
You may not be able to go to a pricey doctor but you should find a clinic or a VNA that works on a sliding scale. Do that so you can rule out heart desiese. Then consider that your back is out, because of your anxiety your muscles tense up and pull your back and chest muscles too tight. If your chest hurts worse when you press or run on it then it is most likely muscle tension and not a heart attack. Make an appointment with mental health (they do sliding scale or get goverment assistancefrom DFS) and get on some anti anxiety meds then go see a chiropractor. I've been suffering from Anxiety forever- I walked into the office with chest pains and I walked out pain free for 9 months. Also consider if you have anxiety that drnking alcohol will really make it 100 times worse becasue of the chemical reaction it has as a depressiant and a diuretic. if I drink I get a full bloen anxiety attack - racing heart and chest pains. Drugs do this too, Hope this helps.
Anxiety symptoms can change. It could be any number of things. Without knowing anything about your lifestyle, diet, etc. it would be hard to even guess. Your heart is electrical so you emotional issues may have shifted to another level. If it is a serious heart problem, you won't know unless you get a diagnosis. So you wait and see what happens, go to a doctor, or try some zen like activities to see if it makes a difference, like mediation, yoga or whatever seems interesting to you. Right now you are fearful because of the unknown. Many things can be happening. A virus can trigger that type of pain also. Don't your parents have insurance? With the Obama plan you can still stay on theirs until you are 26.