Last night when i got home i started shaking, i was nauseated and i had a headache. my heartbeat was fast. what could be causing these symptoms?

Possible: its tough to tell without a full history and physical. It could be the rate caused your symptoms, its more likely the underlying problem caused the heart to go fast. this is called a reactive tachycardia. simply put ,when the body is "stressed" the heart reacts by increasing it rate. sounds like maybe you have a viral syndrome like the flu that set thing off. see your family doc.