Low progesterone is something that would be a diagnostic sign of you not having ovulated, rather than a cause, if that makes sense. Progesterone levels typically go up after you ovulate - the corpus luteum churns it out to support any pregnancy that might occur - so if your progesterone level is low it suggests you haven't ovulated in that cycle. It's not terribly unusual for women to have the occasional anovulatory cycle (I managed to have one in the month I had a day 21 progesterone test done, so my clinic thought I just generally didn't ovulate - but actually, I generally do and just didn't that one time!) but it's definitely worth getting checked out to see whether you have pcos or any other issues, especially since you're feeling so grotty.
It sounds as though you have upcoming appointments, so hopefully you'll get some answers - in the meantime, look after yourself and try not to stress. Good luck!