Progesterone and pregnancy

As if this pregnancy hasn't scared me enough, from the baby measuring smaller than predicted, testing of beta HcG levels. Thinking I've been dodging one bullet after the other, I get a call from my doctor's office saying that my progesterin levels are low and needed to be supplemented in order to carry this pregnancy full term. Reading sometimes is so detrimental because once I did my own research, not only did it answer a lot of questions to some pre-pregnancy symptoms I had been experiencing but the thought of having this go untreated and potentially leading to miscarriage was enough to devastate me. I start taking my pills tomorrow and I'm keeping my fingers crossed that my first sonogram next week goes well. Is anyone else experiencing this or have experienced low progesterin? If so, what was the outcome?