I would make an appt with your doctor to further explore, in addition to the info by the above poster it would be a good idea.
Pulsate with the heart rate?
Do you have graves?
There is something called a thyroid bruit which is a vascular murmur heard over a hyperactive thyroid gland due to increased blood flow to the glands.
whether you can feel a bruit,I don't know,but it could be causing it.
Its usually found in graves patients.