I suddenly started having an increased heart rate with chest pains and shortness of breath. no clots, and not caused by meds? what could cause this?

3 letters: SVT: Very common in your age group for these symptoms is svt, a rhythm condition in which the heart suddenly races. Switches on/off. Called supraventricular tachycardia, rates up to 180-210 beats per minute sometimes seen. It can be hard to catch: needs to be seen on an ECG for diagnosis. Best test is a 30 day event recorder, a device you lease for a month and which can be switched on when occurs.