Heart beating very hard past 2 days. Can feel/hear blood pumping into my head, even feel it in my teeth. Giving headache and nausea. Causes? Serious?

Consult MD. Your blood pressure should be checked and a md should be consulted to rule out a serious condition.
See PCP. You should schedule an appointment with your physician as soon as possible to determine why your heart is racing. If you are not over exerting yourself, your heart should not be racing.