Yep absolutely you can be tested when not pregnant. Progesterone is important for implantation so needs to be there before an actual pregnancy so to speak. If you have mid cycle spotting or a lot of spotting before a period it can be an indication of low progesterone, this is what I had & hence the CD21 progesterone test. I also had a lot of symptoms of low progesterone as well - low libido, cold body temp, anxiousness & irritability. It turned out my progesterone level was fine, but the symptoms ended up being linked to hypothyroidism which causes the exact same symptoms & also hampers implantation.

So maybe look up estrogen dominance or low progesterone & see the list of symptoms, some might ring a bell for you. Also if you're charting your cycle & your temp is dropping well before AF it might be showing something there. It's a simple BT 7 days after ovulation, but most times you'll do an ultrasound around ovulation to confirm you are actually ovulating before worrying about the progesterone as it won't be produced properly if you don't ovulate.