Hello and thank you for using HCM. I carefully read your question and i understand your concern.Don t worry, its nothing serious. This feeling of not getting enough air might happen for different reason. Sometimes just a simple stressful situation, anxiety can cause this symptom. All sow a fast heart beat, an extra systolic-heart beat might gives this sensation of not getting enough air. This tachycardia or extra-sistolic heart beat might be quite normal, to come and go, or might happen because of a different pathology, an anemia, hyperthyroidism ect. But you explain taking a medicine with this side effect. If it is sow, you have to wait for some days, minimum 48 hours for this effects to rebound. The time depends from the kind of medicine, for how long does it totally eliminate from your body. So, just wait for some days and see. If you have the symptoms again than take a look at you rhythm when you feel this breathing difficulties. Only then, you might do a simple electrocardiogram, an echo-cardiography and maybe a holter monitoring. This can show us better your heart structure an rhythm tendency. Hope I was helpful. BEST REGARDS.