It seems like your fitness and nutrition is spot on. You´ve got your physical health spot on.
Witch leaves the emotional aspect. Have you considered that this might be an emotional state? Because this sounds a lot like depression. The thing about emotional states, is that we´re not always aware of them. When was the last time you were totally enthusiastic? And did you feel more energetic then?
I´ve learnt a few things about emotional stuff from the sedona method. On the lower end of the scale, is apathy. When your in the apathy emotional state, the body is in rest, and you have no energy available.
And now I´m gonna be rectum and raise the question, "mayby it´s a belief issue?". If you felt like this for a time in the past, maby you reinforced how you feel by repeating the lack-of-energy-story like an affirmation?
Or, in the case of affOrmations, you ask questions that forces the subconscious mind to give you an answer, thereby reinforcing the belief. Like "Why am I so tired all the time? Why do I lack energy?". A bit of googling on Noah St. John may help to understand the concept.
Anyways, it´s only food for thought to stimulate some problemsolving. When the physical body is in shape, maby it´s not a fitness/nutrition issue.