have you had an ultrasound on your heels at all? I have plantar fasciitis and it sounds very similar to what you are describing. If the pain is most extreme immediately after rest once you put weight on your feet again (and its usually excruciating) then it could well be. plantar fasciitis is inflammation of the plantar fascia ligament with inserts at the heel bone and attaches at the other end of you foot sole (again to bone) if the ligament has lost its elasticity (a degenerative condition) then it will shorten with rest and tear when weight is placed on the foot again. heel spurs will eventually develop as the body tries to compensate for the shrinkage in the ligament by growing new bone at the ligament insertion point in the heel. It is not uncommon to feel as though you have jumped of a rooftop and landed on a small stone right on this part of the heel (very very painful) it will usually ease somewhat with movement (once all the tearing is over) but with prolonged standing the pain can be likened to having someone belt the soles of your feet with a baseball bat an ultrasound will easily confirm whether or not your plantar fascia ligament is inflamed. the treatment options are limited in their effect. you can get a proper gait scan done and spend a small fortune on orthapedic insoles to correct the flattening on the sole of your feet, a special method of taping commonly used by physiotherapists will provide some relief, or you can get an ultrasound guided steroid injection (of course the need for all of these will be determined by your doctor)
really feel for you foot pain is a real bugger - there is no way to really avoid the aggravation caused by putting pressure on them especially if you want to get from a to b like getting from the bed to the toilet.
by the way i have not found any pain medication including narcotics to be helpful for plantar fasciitis in any way - im not really sure why the drugs have no effect? but for me at least they do absolutely nothing
i hope your doctor can get to the bottom of the cause for you really soon.
all the best!