I woke up this morning with the classic symptoms of fibromyalgia, achy everywhere. Is that what I have?

Not necessarily. Fibromyalgia requires constant pain for at least 3 months. Many things can cause you to wake up feeling achy, including viruses but these causes are usually short lived. Also, if you didn't sleep well it can cause the same symptoms as fibromyalgia. Give it some time or get a new mattress if it's more than 5 years old. Follow sleep hygiene recommendations to improve your sleep.
Unlikely. Fibromyalgia is a chronic condition, one that goes on for more than a few days. If you have these symptoms for one day only it is unlikely to be fibromyalgia. A viral illness can give you the same symptoms.
No. On waking "achy everywhere & classic fibromyalgia (FM) symptoms"; is possible? No! FM has insidious onset & evolves over time due to precedent soft tissue injury/disorder. FM etiology is elusive due to remoteness of inciting event(s), which subtly conjoin as co-factors in multifactorial causations expressed in an unstable body tower (beset w. loose pelvis) subjected to repetitive gravity stress.