Multiple sclerosis is the disease of nervous system. The patient lost his myelin sheath of neuron. Usually in MS patients some lesions are present which are supposed to be related to MS. But there are chances that MS patient show no lesions on MRI. The lesions in MS patient continue to grow and degenerate. It may or may not be present in MS patient on MRI. The problems you are reporting can be due to the side effects of medicine you are using.