I had low D and low iron that I remember.
I had AI and I too suffered from very low Vit D and iron.
Also you say you suspected you always had low testosterone. Please do not confuse (as many do) low testosterone with low libido. They are not the same.
my testosterone was low several years ago--i got it up with a T-cream---but for some reason my body can't maintain it, and it can't maintain the DHEA levels, either
I just take DHEA pills. A decent brand helps me - but I do fluctuate a lot. Even on my E-patch, I still can vary.