Hello from JustAnswer.
This is actually a complex question.
Many of the symptoms that occur with depression can also occur with fibromyalgia, particularly depression, muscle aches, fatigue, and difficulty sleeping. Statistically, it is more common to see depression with chronic muscle aches than fibromyalgia with depression, but either is possible. There actually is a third condition that also has overlapping symptoms, called chronic fatigue syndrome. Trying to differentiate between these three conditions can be very difficult. And there are some theories that there is similar underlying brain dysfunctions in all three conditions.
The diagnosis of fibromyalgia is based on the findings of certain tender spots in characteristic locations, called trigger points. However, part of the differentiation is related to the predominant symptom. So, someone that is more bothered with depression would be diagnosed with depression, someone with a predominant symptom of muscle aches would be diagnosed with fibromyalgia and someone with a predominant symptom of fatigue may be diagnosed with chronic fatigue syndrome. Similarly, if one symptoms started significantly before the other symptoms - depression, muscle aches, or fatigue - then that may guide the diagnosis to the respective condition.
So, it is more likely that you have depression, but if the muscle aches are becoming a predominant symptom, it is reasonable to discuss this with your doctor and your doctor can examine for the presence of characteristic trigger points.
If I can provide any additional information, please let me know.