Testing for progesterone (specifically P4) is done on 7DPO. That level at that time interval will determine if ovulation actually happened and if it's high enough to sustain a pregnancy. I wouldn't mess around with waiting, especially if TTC with low prog.
I will TTC again next month, after our 15 week loss in May. I had low progesterone and bleeding issues the whole time--although not necessarily a loss related to low prog. (we did not do genetic testing), but combined with it being a twin gestation and starting supplementation too late, I just don't want to take a chance. The 2ww of every cycle we TTC here on out we'll start supplementation.
Good luck, mama!