i don't know what the problem might be but my first thought was that you should make an appt with your pcp.

not all problems are MS related. maybe there is something else going on and that problem is flaring your MS sx's.

mid back pain can sometimes mean kidney issues. i wonder if you have an infection?

i hate it when drs don't think outside the box and just brush off complaints and sx's as not being real. generally pain signifies something. pcp's/internists are usually better at the diagnostic problem solving issues.

please let us know how you are.