An urgent care can't help with a heart attack. They can't diagnose it or treat it. If you think you are having a heart attack you must call an ambulance.
Go to another hospital and demand they check your enzymes. They may come out in the normal range, this happened with me, and you can still be having a heart attack. Stay there until they find out what's going on. You're very young and the blood test did say you have an infection so chances are it's not your heart. Still, it's always better to be safe when we're talking about a possible heart issue. I'm leaning towards a possible lung or chest infection but please go to another hospital.