Ive been having headaches heart palpitations and excessive hungerwhat causes it?

These are vague symptoms that can be caused by several overlapping single entities or separately by two or more. Write down all your symptoms with a timeline and take the list with you to a visit with your doc. They can review your past and current history, do an exam and tests & determine how best to proceed.

There is not enough detail here to be able to tell what is wrong. You should see your primary care physician, who can do a more complete history and performing physical exam, and help determine what the next steps of the evaluation should be. Good luck.