There are a variety of adrenal support and thyroid products out there on the market that can help you, there is a whole alternative health system out there that can help you get better, you just need to know how to use it.
For instance, look at some of the standard process products or thorne. The drenamin product could be one that might work, its rather safe in general at low doses. You also could be deficient in iodine and if you supplement with it, it gives you energy (standard process makes one).
I personally think your recent symptoms are thyroid related, but thyroid testing can be inconclusive. I would consider testing your iodine levels to see whether they are low or not.
Then there are some other products to look into as well. Digestive enzymes help you gain more energy from the food you eat, by allowing your body to break down and absorb the food better. These are rather inexpensive and likely would help you pretty fast.
S. Boulardii is something else I would look at as well as kombucha. Boulardii is highyl anti-inflammatory and produces lactic acid. Kombucha has a variety of b vitamins in it that help your methylation system and overall energy.