HCG levels ok but progesterone levels low?!

On Thursday I had my first visit. Based on the measurements I’m a week behind then what I thought I was based on LMP. I was supposed to be at 6weeks and 4 days but instead I’m 5weeks and 3 days. I got blood work done and yesterday I was informed that HCG levels are ok but my Progesterone levels are low!!! What does that mean? Should I be concern? Anyone else been through this or going through this? I started on the Progesterone pills yesterday but I’m freaking out. Trying to stay calm but it’s difficult. I lost my baby girl at 13 weeks and this is my rainbow baby. I pray that everything will be ok... Going back in two weeks!!