Sorry to hear about your doldrums.
There are two possibilities: 1. you are burned out from cycling; 2. you are serious depressed...no I am not talking about simply being in the dumps mentally...I am talking about the real deal...you may have a serious chemical/hormonal imbalance in your brain that may only get worse...I am talking about clinical depression.
You need to go see a doctor and get tested/evaluated. It's one thing to be down for a few days...it seems your situation is far worse than that. Don't treat your problem as if it's some common cold or flu you can get yourself over by yourself...this sh*t is so serious, I would say it can be just as bad as something that would require invasive surgery.
Go see a doctor...take it from someone who has experienced this before.