I had severe chronic pain long before i was dx with MS, I have reflex sympathetic dystrophy ( cmplex regional pain syndrome) as well as phantom pain from a through knee amputation. I tried just about everything of pain including grass, all grass did was increase my appetite ( a not needed effect since i also have a weigh problem!).
I eventually went to a specialist Pain clinic, they tried various combinations of drugs including oral narcotics but even very large doses had only minimal effects on the pain, the down side was also that they made me so out of it that i could not really function adequately in day to day chores etc, i could not work and could barely care for myself. Then they tried a long term epidural porta cath- i injected the porta cath with a low dose of morphine and the local anaesthtic marcaine, 3 times a day- it gave great relief with minimal side effects and none of the euphoric, dopey side effect of narcotics. Unfortuantely after about 18months i built up scar tissue in the epidueal space ( about 10% of patients get this apparently) so it no longer worked. I was back in pain hell after a really good 18 months. The only real option for me to try was intrathecal medications- eg spinal, its like epidural but goes in through the dural membrane directly in to the fluid around the spinal cord. I have a synchromed pump ( the same kind used to deliver Baclofen for som MS er's) and it gives me a small dose of morphine continually. when i was on oral morphine i was having over 900mg a day and was still in pain, but when they put the pump in i only needed 5 mg per day- because it does not go via the circulation and the liver but directly to the are that needs it, you only need a fraction of the dose. I have had my pump for 6 yrs now and while i can't say i am pain free, pain no longer controls my life in the same way.

I would suggest that anyone with severe or chronic pain would be wise to be refered to a pain clinic for assessment, a combination of your neurologist and the anesthetists at the pain units would be better set to assess chronic pain. The Complex regional pain syndrome i mentioned is one thing that can occur if chronic pain is under treated, changes occur in thecnetral nervous system so that pain arises from within the nervous ystem itself and becomes very difficult to treat. I had pain from a leg injury that had been inadequately controlled, had i seen the pain clinic team earlier i may not have developed the condition and may still have my right leg, ( i had the leg amputated in an attempt to rid myself of the severe pain but it was too late, I already had develped the RSD)-