The back inside of my right heel hurts very badly when i walk. this occurs all day. it also hurts when i flex my foot upwards. what could this be?

Sounds like: You might have a problem with your Achilles tendon. I suggest you see a local Podiatrist as soon as possible as you risk further injury. I would also recommend getting an MRI.

Tendonitis or fascii: The pain in the area describe can be plantar fasciitis or Achilles tendonitis. Less commonly can be a stress fracture of the heel bone

Healing the Heel.: More than likely, there is something amiss with your Achilles tendon. It is possibly irritated from over use or potentially partially torn. It is best to protect the area with a boot and minimize the stressing of the tendon until it can be evaluated. Now id the time to consult with a specialist.

Achilles tendonitis: haglunds or retrocalcaneal spur…..get X-rays and your doctor should be able to decipher..