Enlarged lymph node behind 1 ear. The lump feels warm, throbs, on/off pressure in head & lightheadedness, only sleeping few hrs at a time, and fatigue?

Enlarged Lymph Node. A hot, painful lymph node such as you describe usually signifies it is draining an infection in the area, or is part of a systemic lymphadenopathy, of which there can be many. I would definitely schedule an appointment immediately with a doctor to undergo a thorough evaluation to pinpoint the source.
See a doctor. See a doctor . You may have developed an abscess. Behind your ear. Treatment is in order.