If you have atrial fibrillation that is not well-controlled (i.e. the medication is not working), this can lead to some of the symptoms you describe due to a fast heart rate, which causes the heart to not work efficiently. The symptoms can be due to the atrial fibrillation itself or another underlying heart problem that led to the atrial fibrillation. I would suggest talking with your doctor about your symptoms and to discuss whether additional therapy is necessary for your atrial fibrillation-there are many options to treat this disorder. He or she can also determine if additional testing is warranted.