Both of my family member who are in remission had ME/CFS for about 5-6 years, although both had mild cases for most of that time. My daughter was seriously ill for about a year before she started Valcyte. I wouldn't say pain was a major factor for either of them, but I know my daughter had muscle aches, but no severe pain.
Valcyte is incredibly expensive. I seem to recall that it cost about $50 per pill, so $150 per day. So for two of us taking Valcyte at the same time it was over $100,000 per year --- for two years.

I would certainly apply for patient assistance if you're eligible.

Insurance may also cover it if the reason for treatment is given as CMV or HHV-6 infection.