I don't know what you mean by "ns" or training your "ns". The cause or causes of fibromyalgia are not known to medical research. You will see that if you do some research into the condition from reputable sources. It can't be self-diagnosed - it is far too complex for you to do it yourself. You would need to see at least one, maybe more, specialist medical consultant(s) who would perform extensive testing to rule out/in countless other conditions or problems that can be similar. Have you been formally diagnosed with the condition by a specialist doctor?

Just training the same muscle group twice in a week, even lifting the maximum amount you can, would not cause fibromyalgia. You may just be overtraining or have a weightlifting/training programme which is unsuitable. That alone can cause pain, fatigue, stress on your immune system and all sorts of other physical issues. I honestly think you will keep having problems if you don't get some specialist assistance with your training to help you identify your training goals/outcomes and the most appropriate way to work towards these.