Hi, Chikatz, and welcome! You know, a bagel is loaded with carbohydrates which can raise your blood sugar and cause you to be very tired. If you eat a lot of carbs, you will be more tired. Here is a link about bagels. One bagel has 70 g of carbohydrates!
We won't even discuss what you put on top of that bagel! 
http://www.livestrong.com/article/360203-the-carb-count-of-a-bagel/
I find that if I eat fewer carbs, I have a lot more energy. I'm diabetic and so fruit will do this to me, also...not to mention all the goodies we crave from the bakery and ice cream shop. But if I stick to eggs for breakfast with one slice of low carb bread toasted (I use White Wheat) and a few strawberries, I have energy all morning long. The eggs have a lot of protein in them and that gives you energy.
I know that if I watch what I eat, I don't have nearly the fatigue that I will have if I cast my fate to the wind.
You do need to keep moving with fibro or you will be stiff as a board and have more pain. I do gentle exercises, walk daily, and pace myself when doing things. All this helps with the pain and the walking actually gives me more energy too! So, you might give that a try if you haven't already.
Be sure to read Fibro 101...the first thread on the forum. There are links to good info about fibro and you will learn a lot there. Good starting links are called Symptoms, What Else Could It Be, and A Thorough Explanation of Fibromyalgia. You just might see yourself there.
I'm looking forward to getting to know you better. Don't hesitate to ask questions because we are here to help you. Hope to hear more from you soon.
Sherrine