Hello and hope you are doing well.
You must be having Sinus tachycardia. Normal sinus rhythm (NSR) is the characteristic rhythm of the healthy human heart. The normal regular rhythm of the heart set by the natural pacemaker of the heart called the sinoatrial (or sinus) node. Sinus tachycardia can occur with anemia, anxiety, hyperthyroidism, fever and dehydration. It may not be related to a cardiac disorder. It can be aggravated by exercise, fever, excessive alcohol consumption and smoking. So, please don't worry and discuss the possibilities with your consulting doctor.
Hope this helped and do keep us posted.
To try to put your mind at ease, do you have any history of heart disease in the family? Are you a smoker, overweight, drinker or have high blood pressure?
If you are in generally good health, and eat properly, don't smoke or drink often then it could be normal the chest pain could be non-cardiac depending upon where it is, its difficult since you can't see a doctor with no insurance (I know where you're coming from) but if you are experiencing such a high heart rate after climbing ten steps, then I would say you could be deconditioned, but when you exert yourself do you get any chest pain? If you do, what type of pain is it?
Perhaps you can go into a walk-in clinic if you are really concerned over this.
Best regards. ;-)