You know, on reading some more of your details, I'm thinking perhaps it's not physical energy but stress and mild depression that's your problem? Sometimes people think depression is this active really "sad" thing, but really it can be a simple an description as your whole system is (slightly) "depressed" and it basically sneaks up on you when you get lazy looking after yourself. It's a physical thing that affects you emotionally but a little daily sunshine, light excercise, plenty of water, avoiding caffeine/sugar/fat, and sleeping regularly go a long way.
And I think you could benefit from the opposite of jumping your system and do meditation/yoga instead. You know 'mindful' exercises. And keep realistic to-do lists. Watch a funny movie or call an old friend every few days. Do things that make you chuckle and you look forward too.
It's small steps and consistency that beat routine depression/sluggishness. 30 minutes of light exercise a day works -- walking outdoors is the easiest, cheapest thing you can do and quite effective.
I've also struggled with energy levels. I'm normally extremely energetic to the point of hyperactive (I can seriously be too much for extreme introverts, like my INTP brother) but I've had mood/stress/avoidance issues and self-medicated through effing up my sleep patterns to the point of FUBAR and caffeine/stimulants. ---> Not the way to go. Caffeine and other stimulants will seriously eff up your system and it's not true energy nor will you be clear headed.
After a lot of trial and error and research, I think barring medical intervention, slow, steady, and consistent is the way to go. Though getting a full physical is a good start too. Or talking to a trainer and getting an initial assessment.