You definitely need to make sure it is your testosterone making you tired before taking any supplementation for it. Just because something is natural doesn't mean it is safe, as you well know, I am sure. Definitely get your thyroid checked out. Even if levels come back normal, you may supplement kelp or irish moss to support your thyroid and give you energy. Hope you find out what's going on. Stay healthy!!
I once took androstenedione (a steroid precursor) over the counter for weight lifting. It gave me acne after about a week, which is a common side effect of steroid use. So the stuff out there can be potent---and potentially dangerous.
I don't know if Tribulus or Testosterone Fuel raise testosterone or if they are safe. Testosterone supplements, i.e. anabolic steroids have been linked to cancer, liver and heart disease. Don't know if that applies to these over the counter products, but given they have no proven benefit and serious possible risks it's probably best to avoid them, in my humble opinion. Also, artificially elevating testosterone over time can actually result in decreased testosterone as the body's way of compensating.
There are some supplements which are probably safe to use without a doctor's supervision, but I don't think these fall into that category. (Then again I knew pretty smart guy who felt perfectly comfortable injecting veterinary steroids).
Also, although low testosterone can cause fatigue and depression, low energy does not necessarily mean you have low testosterone. In fact at your age it's probably unlikely unless you've been told so by a doctor.
If your energy levels have fallen since beginning working out perhaps you're overtraining, but there could be a million other reasons. If it's a serious problem you may want to have a doctor check your thyroid. I'm no expert and these are just my two cents, but best of luck in finding your lost energy and keeping healthy.