What couldit be

I am a 45 year old female who developed mobility problems during and following her last pregnancy in 2000. I first noticed weakness in right leg on walking and gradually the distance I could walk got less and less. I have had episodes of numbness in the right leg and legs feel heavy. In addition I suffer with muscle spasm and cramps in both legs and now mobilise with a crutch for short distances. I am unable to stand for long periods and fatigue is terrible. Mri of brain and spine were normal but I have oligoclonal bands in my csf. Emg was normal as was visual evoked response. I was diagnosed with ms but this has now been retracted and given a ? functional neurological defecit. All tests that mimic ms were negative such as lupus , lymes. The only other thing positive was a vitamin b12 deficiency which I now take monthly injections for and a bone scan had uptake in spine,ribs, knees, shoulders and sacroiliac joints. Any ideas would be gratefully received or am I mad!!!