is Effexor- commonly used as an antidepressant. Recent findings suggest serotonin and norepinephrine are associated with regulating and reducing feelings of pain that come from the body. An imbalance of these chemicals is also known to cause depression. There is a strong link between pain and depression, and specifically between fibromyalgia and depression. As you do your research you will see this come up over and over again.
I'm not not suggesting you're depressed, and even if you do have a depressive symptoms they are likely a symptom of the fibromyalgia- not a depressive disorder. Anxiety, depression, insomnia, cognitive problems, all traditionally thought of as "mind" problems, are often the result of physical illness and disease. You cant overlook the mind/body connection.
I hope you have a physician who is sensitive to this and will treat you as a whole person rather than just the symptoms of a disease.
I'm glad you can pin a name on your symptoms now. That must be a relief for you. Good luck on feeling better.