What could be the cause of my extreme heel pain?

Heel pain. Your heel pain could be due to many things, most likely it is due to plantar fasciitis or an inflammation of a ligament on the bottom of your foot that attaches to your heel. Of this pain has been persistent you should seek medical attention to get an accurate diagnosis.
Plantar fascitis. Heel pain on the bottom of the heel is usually due to plantar fascitis. It can usually be successfully treated with stretching, deep tissue massage, otc arch supports and nsaids.
Plantar fasciitis. The most common cause of heel pain is plantar fasciitis: an inflammation of a thick band of tissue that helps hold up the arch of your foot. It attaches to your heel bone, and is usually the most painful during the first few steps in the morning, or after sitting a long time and then standing quickly. Check with your podiatrist to rule out nerve damage, stress fracture, or other bony problems.