I also have a fairly severe case of fibromyalgia.  Since my children
were all adopted and needed to be supplemented anyway, it is a bit more
difficult to tell what effects the fibromyalgia had on my milk
production.  However, I strongly suspect that it would tend to reduce
supply, maybe mainly by inhibiting let-down.

I have noticed that when my muscles spasms are especially bad, I do not
experience let-downs at all.  I have also noticed that at the times when
I have felt the worst, my babies have needed more formula from the
Lact-Aid.  Since muscle spasms and pain are the primary symptoms of
fibromyalgia, and relaxation is generally very difficult, I think it is
reasonable to think that it would have some negative effect on milk
production.

One thing that helps me is trying to have the babies propped up to
breast level without me having to do anything to hold them up.  My
shoulders and arms are among my worst areas and holding a baby up, and
also having my arms in the same position for a long time are very
aggravating.

I would think for the mother Robin spoke of that supplementing at the
breast is a good idea, especially for now.  But it may also help her
milk production to prop the baby and do everything she can to help
reduce the pain and spasms, like deep massage, hot and cold packs and
maybe trigger point injections.  I also wonder if she is taking any of
the medications that are typically helpful, or if someone has told her
she can't take them because she is nursing.  One of the most useful is
amitriptyline, which can be real important since people with
fibromyalgia typically have a very difficult time sleeping which, of
course, does not help the milk supply either!

Aloha,
Darillyn