May was my first cycle of Femara/letrozole, I was on 2.5mg CD 3-7. I got my BFP on 10 DPO, I went for labs that day and my progesterone was on the low side so they put me on 200mg of progesterone (Prometrium generic) vaginal suppositories (boy those are fun). My labs also found that my HcG was only at 6. Four days later, 14 DPO, more blood work showed my HcG had only gone up to 9. They thought it was likely not going to stick but wanted me to keep taking the progesterone and come in two days later today, 16 DPO (today). Based on my pregnancy tests, it looks like it was a chemical but blood work today will confirm. I had another chemical in November and other than that have never been pregnant. Has anyone had similar experiences and have a positive outcome?