Appointment 8/29

My first appointment was yesterday. As I expected a lot of blood test were done one of which was progesterone levels. I've never have gotten my progesterone levels checked because I tend to miscarry before my obgyn gets to see so usually I just get my hcg levels checked to make sure they get back down to 0; however today I receive a call from my doctor stating that my progesterone levels are to low and that he was going to prescribe progesterone pills. Can someone enlighten me on this, this is all too new to me and I'm very much concern what does this mean???