Sometimes this is a reaction to antibiotics. If you took steroidal meds, it can also be a reaction to that. It's not fibromyalgia from what you describe, and don't go Googling symptoms as that's a recipe for trouble. Get your parents to take you to the nearest best health food store and buy the best probiotic they have in their refrigerated section to try to replenish the organisms any antibiotic or steroid might have killed off. Eating foods that are fermented or cultured, such as kim chi or sauerkraut, can also help with this. Try to avoid pro-inflammatory foods for awhile, such as dairy, wheat, and sugar. I don't know what meds they had you on, but pneumonia is a tough disease and takes a while to get completely over. Starting a slow easy exercise program, such as walking, might be beneficial. Another thing to think about -- you're 15, how are your hormones doing?