SIBO- Small Intestine Bacterial Overgrowth - Welcome
This site has some good information about what SIBO is and how you can test for it.
What I did is get a test kit from the doctor's office. I had to send it in with payment ($135, not covered by insurance unfortunately) after doing it. The kit includes diet instructions. I had to follow a certain diet for 36 hrs prior to the test, and fast, only drinking water, for 12 hours immediately prior to the test. I timed it so I slept for most of those 12 hrs

. The diet is much like a low-FODMAPs diet, but with some differences. The major things were no starches (but some squash and melons were allowed), no grains (but white rice and popcorn was allowed, as was corn or rice based cereal), no dairy, and very limited vegetables. An intro GAPS diet for three days probably would have worked for it (since that's mostly broth and meat, I think).
The test itself consisted of exhaling normally into this tube with a bag attached, after holding your breath for 5 seconds. Then you push a tube into part of the tube you breath into and it captures some of the air you exhaled. After the first tube, you drink some kind of sugar solution that's provided, and then repeat the tube-breath process every 20 minutes for 2 hours. After that, you can eat and drink. No exercise, food, or water during the test. I forgot to hold my breath before taking most of the samples, so I hope it comes out okay. The test is supposed to measure different gas levels that are being produced in your gut. That indicates whether there is an overgrowth of anything in your intestines. Too much hydrogen, or methane, for example.
I had my hormone levels tested sometime last fall. They took a blood sample 1 week prior to when I expected my (very regular) period. That is when you ovulate, roughly, and progesterone should be high. Mine was very low, all other levels (estrogen, testosterone, something else that I have forgotten) were in a normal range. I began supplement Vitex/chasteberry, which gets your body to produce my progesterone. I experimented with the dose a little and found that it gives me a lot more energy than I had before. I also experienced a spike in libido (considering it was practically non existent before, that's awesome for me). I'm hoping that I won't need to supplement this for more than 6 months and that my body will be producing enough on its own whenever I figure out this gut thing. I'm sure they're linked somehow, though I can't say how.