How to talk to your GP about Fibromyalgia

How do I start the conversation with my GP about Fibromyalgia? Ive had TMJ disorder for years but in the last 2 years had really bad pains in my head neck back and legs which can’t be relieved with my painkillers (pregabalin) but my GP keeps brushing off the idea of fibro even though it’s prevalent in my family. Just feels like it’s getting work and the fact that nobody is taking it seriously is getting me down.