Hi...I am a 28 year old professional who has lately experienced some strange symptoms. I have been experiencing extreme weight gain (10+ lbs.) and loss over the last few months. In addition, I am constantly tired and light headed. My body feels fatigued no matter how much rest / sleep I get. I have a fairly healthy lifestyle in which I exercise regularly and eat semi-healthy. I also experience shortness of breath at times and have trouble swallowing. My younger brother had thyroid cancer a few years ago and I am wondering if these symptoms could be something that serious? Please advise!!