I'm short of breath just from going up the stairs, ecg, d dimer, and chest x ray all come back normal! could it be a blood clot still or could it be due to changing my pill?

Need more tests: The three tests you describe are by no means a complete enough work-up based on the severity of your symptoms. You need to rule out both a cardiac cause with a BNP level and an ECHOCARDIOGRAM, as well as a pulmonary embolus with a "V/Q" scan or a CT pulmonary angiogram. If your symptoms are indeed sudden in onset and this severe, I would go to an emergency department and get tested there.