I have a resting hr of 104. i have been exercising a lot today and when i do, it goes up to 137. i get lightheaded and shaky during exercise. causes?

Fast heart rate: Check with your primary doc first. Important to check to make sure you don't have anemia, hyperthyroidism (excess thyroid hormones), not drinking too much caffeine. Get a echocardiogram to make sure you have no structural heart disease. If everything checks out negative, maybe worthwhile to do a plain EKG stress test to make sure your heart is responding appropriately to exercise.