Abnormal sensations are perfectly normal when having MS, these are referred to as sensory symptoms and yes, they are nerve related.
Your wedgie sensation is probably one of those normal abnormal sensations thanks to MS.
I have had some pelvic issues this pass month with trouble going to the bathroom and odd buzzing down there.
Many women who have MS tend to freak out the fist time they experience buzzing/vibrations in the girlie parts. I have had buzzing/vibrations from the waist down as well as in the girlie parts.
I am betting you have spinal cord lesions. Spinal cord lesions tend to be more symptomatic than brain lesions and cause symptoms from the spinal cord lesion...down. Spinal cord lesions can cause bladder, bowel, and pelvic issues, problems with mobility as well as other symptoms.