Increased heart rate, dyspnea. Can help.

I am 18 years old, and 123lbs. I have been taking 40 mg of Vyvanse daily for ADHD for 2 years. My average heart rate has always been on the higher end, 80-90 bpm. Randomly I will have spots on my body, such as feet and knees, turn red, burn and itch. Recently I have noticed that after walking a short distance, I will have shortness of breath, sweating, and turn red (This is not normal for me). Over the past month or so, I have noticed my heart beating faster (110 bpm at rest) and harder, sometimes accompanied by arrhythmia. This randomly occurs throughout the day, but consistently occurs about an hour after taking my medication, and is accompanied by sharp chest pain. Also unrelated to the increased heart rate, at times my legs or hands will involuntarily, shake slightly. I do not know if all of these symptoms are related to each other, but they are all abnormal for me. My current doctor seems unable to tell me the cause of these symptoms, hoping you can help. Thanks.