My heart is racing and feel dizzy when walking up stairs?

See a good physician: I assume a small number of stairs. You may have an abnormality of the conduction system that regulates your heartbeat. It may be apparent on an ekg or perhaps an exercise ekg may demonstrate a problem. Of course, other problems could also be the cause, such as a malfunctioning heart valve or a congenital abnormality of the heart. You are young and need to see a good physician.