Hi Sarah.
Have you been diagnosed with fibromyalgia? If not, that exploration is your first step, and I advise you to make sure it is a thorough exploration, meaning you get tested for all of the things that could cause your symptoms. There are many, and you need to find out to the best of your, and your doctor's, ability what exactly is going on with you. (If you don't already know).
As for fatigue, and its prevention or management, this is a bit different for everyone. I see you have already read my big post of advice for newcomers. The best thing you can do for yourself is to start that personal journey of experimenting with your self to find out what kinds of things work for you in terms of diet and exercise and so on, all that I wrote in that post.
Of course, sleep is very important, so whatever you can do to get enough of that in terms of timing, your bed, your pillows, even your sheets, is good to try. I make sure my bed is as fully comfortable as possible. I spend the money for good quality sheets and pillows, for a memory foam mattress cover, and I live where it is very dark and quiet at night. That works for me; other things may work for you.
Diet and exercise can also help tremendously with your fatigue levels. But unfortunately, although lots of people can tell you what they are doing that works............and that's valuable information to get..........only you can find out what works for you, because there's no one thing that works for everyone with fibro. What we can do though, is be supportive of your process, so stick around.