Thanks for posting your query.
With the available described symptoms, there appears to be possibility of paroxysmal arrhythmia's.
Presence of racing heart beat along with lightheaded suggests the diagnosis.
You should immediately consult with internal medicine specialist/ cardiologist and should go for thorough check up.
You should go for electrocardiography
on preliminary basis.
You should also go for holter monitoring along with electro-physiological studies of heart.
you should take proper medicines for control of arrhythmia.
Dr. Mayank Bhargava