Why when I get up my head pounds really fast followed by a fullness feeling. Also I get tachycardia in which my heart rate goes up really fast pounding hard to back down to normal than a minute later it goes up fast again then back down. I had an EKG once that found rbbb. Is that serious?
Tachycardia can be due to multiple problems like anxiety, anemia, thyroid variations, stress, Chat Doctor.  BBB is physiological most of the time, even can cause tachycardia. You can consult the cardiologist and get evaluated. All the best. Take care