Bad headaches for 2 weeks on and off, nausea, dizziness (not vertigo), fatigue, increased heart rate (at times). blood tests normal. not pregnant.

Headache : Does your headache radiate around your head or is it located in one place? Do you have flashing lights in your eyes when you have the headaches? Of you do, you could have migraine headache. That is called the prodrome. If it feels like a band around your head, it could be a tension headache. I hope this helps. I need a little more history to fully help you if it continues, see family doc.

See a neurologist: If the headaches are severe and episodic, you could be having migraines. This in particular, if there are visual symptoms such as flashing like or if there is sensitivity to light. A neurologist should be able to help to diagnosis and treat this. You may also need additional brain imaging studies like an MRI scan depending on what the neurologist finds on your physical exam and history.

Statistically...: At your age the most probable answer is a primary headache disorder (migraine/tension), now frequent and bad because driven by something (stress, hormones, other). However, this is a statistical statement. The problem with diagnosing by symptoms alone (no test findings) is no proof, and sometimes the right answer is the improbable answer. Need formal evaluation.