@chestert6 , Everything that
@SBee says above is similar to what I would say to you, and all of it is very good advice.
I think the most important thing, when dealing with a condition like fibromyalgia, is to
experiment.
You have to try things, carefully, to find out what works for you. This goes for diet and exercise and supplements and medications and activities such as meditation or relaxation protocols....pretty much everything.
I have found that the things I used to love the very most to do in my life are now not possible for me, and that has been a huge challenge for me. I have learned a lot about practicing Radical Acceptance. But one still has to find ways to keep the body moving.
Many of us find that walking is a good activity. Putting on music you love and dancing in your home is another thing that works for many. You can find thousands of YouTube videos with Pilates, yoga, exercises, and dance on the internet and try them out. No matter what age you are, if you try the ones listed "for seniors" they will probably not be too much for you, and you might be able to move on from those to something more strenuous in time.
Gaining muscle is another thing. I used to lift weights and I loved that. These days, I can't do anything even close to what I used to. I used to work out every day with 15lb dumbbells and a 35lb barbell. These days, 5lb weights are all I can do. I found that depressing at first, but I have adapted to it . If you use even 2 or 3lb hand weights, but do the reps very very slowly, you will build muscle over time. Again, you can look for videos online to help you to do this, because form is very important to avoid injury, even when using light weights.
Whatever you can do, do.
And no matter what it is or how light the exercise needs to be, especially at first, it is very important to
give yourself credit for doing it. Tell yourself that you have done a good job, and do that every time. Might sound silly, but do it. It will help.