AlwaysRosie makes an excellent point about anemia (sp?). I had a friend who was severely anemic. Among her many symptoms were fatigue and depression. She said that she cried a lot and didn't have any energy. She also had some other really strange symptoms; she was addicted to Altoids and to the smell of Snuggle dryer sheets (she had to have them around all the time so she could smell them). She felt compelled to eat toothpaste. None of us understood what was going on; we used to tease her about the Altoids. Then she finally went to the doctor and found out that she was severely, dangerously, anemic. The doctor told her that the fatigue and depression were symptoms, and that the strange cravings were also common. The doctor said that some severely anemic people even eat dirt; they just crave it and can't stop themselves from eating it. After we found out how sick she was, we all felt really bad and just kept apologizing to her. Here she had this terrible condition and we thought it was a joke. Needless to say, we all became very supportive when we found out the truth.
I know that this all sounds ridiculous, but I swear it's the truth; I wouldn't lie to you guys. I guess that the moral of the story is that you never know what is really behind your symptoms. I would take AlwaysRosie's advice and get your iron level checked right away. And while you're at it, have the doctor check your thyroid too. That's the first thing my pcp did when I went to see her about being depressed. She said "let's make sure it's not a thyroid problem."
Keep us posted on how you're doing.