Peripheral neuropathy is a condition in which the nerves of the lower extremities cause pain and abnormal sensations. The word "idiopathic" literally means that the cause of this type of
neuropathy is unknown. It is estimated that 35 to 50% of all neuropathies in the United States are of this type. It sounds like you have been thoroughly examined and tested to rule out known causes of neuropathies, like vitamin deficiencies and diabetes. So, unfortunately, I cannot make any suggestions for you to help slow the progression of this type of neuropathic disease. However, there are many treatments that can be tried to make the pain less severe.
Medication treatment for neuropathies can include your standard pain medications, but most people find that they really don't help nerve pain that much. The majority of people do well using antidepressant and anticonvulsant medications, as they are some of the few medications that reduce the nerve pain itself. Also topical ointments, like lidocaine jelly or capsacin, can help reduce pain and discomfort.
Non-medication strategies for peripheral neuropathy include elevating your legs (to reduce the edema) and keeping your feet warm with some good socks. Eat well and try to exercise if you are able. If you cannot stand to exercise, I know that many public TV stations play chair exercise programs daily, which you can do to help maintain your mobility. You may even need a physical or occupational therapy evaluation to help you get started with walking, as you may need some assistive devices to help your balance.
My last suggestion to you is to make sure you have been seen by a neurologist and to follow the advice that they give you for treatment. Furthermore, you can try to join support groups for conditions like this (for sufferers of chronic pain, for example), which may give you valuable insight and advice on how to live with this condition on a daily basis. I wish you the best of luck.