What is feeling light headed, dizzy & difficulty breathing a symptom of?

sounds like anxiety. sweaty palms and fast heart rate? maybe you shud go to a therapist cuz these symptoms cud be the result of stress, anxiety, depression.

Yes, it's very possible to experience dizziness/lightheadedness associated with anxiety but not during an actual panic attack. It can be associated with a more generalized anxiety. I've had an anxiety disorder and panic attacks since early childhood and I remember dizziness being a common symptom for me for many years during my teens. It's always a good idea to see you Dr. initially and rule out any other possible issues; there are a few things that can cause symptoms that are also common to anxiety: low iron, low blood pressure, hypoglycemia are some of the more common examples. I had low iron during my teens and it was definitely contributing to the symptoms of dizziness. (Young women in the early years of menstruation are more likely to have low iron if I remember correctly) If any physical causes have been ruled out, then one of the biggest reasons for dizziness in people with anxiety disorders is hyperventilation. People who are anxious are more likely to breathe improperly and more shallow. You can test this by lying down and putting one hand on your upper chest and one hand on your belly. Try to just breathe as you normally breathe and take note of which hand rises first when you inhale. If your upper chest rises first, you are breathing more shallow and this can cause dizziness/tingling/etc. It takes a lot of practice, but you can do relaxation and breathing retraining exercises to begin breathing into your diaphragm instead of upper chest (Hyperventilating changes the balance of oxygen and carbon dioxide in the blood and this is what causes all the symptoms) If you haven't read any books or anything, you might find "Don't Panic" by Dr. Reid Wilson and "The Anxiety & Phobia Workbook" by Bourne, helpful to you.

Don't give the doctors any more of your time; they failed!
If all of those tests did not reveal anything, then it must not be medical, but what I would do is first, look at my weight. If that is not a problem, it still could be a heart worm.
Those symptoms point to the heart. Do you have any pets?

hypercondria?