Low progesterone levels

I had my first sonogram yesterday and doc said everything looks normal.  I'm about 5.5 weeks along.  He had me get some blood work done and my progesterone level was 13 something, should be 15 or higher and they want me at 20.  They're calling in a prescription for some vaginal suppository that I have to use nightly for the next 6 weeks with blood work done weekly.   I'm super nervous what this means and my fiancé looked it up and said most women were Fina with medication but I'm scared to really look it up and he mentioned to MC word.  Any ladies with similar results or experience with low progesterone and the medication?