Bleeding after progesterone changes?

ac5278

I'm pregnant with my first child after a year of infertility and countless procedures. Yesterday I woke up to a large clot, slight bleeding, no cramps. I had an immediate ultrasound (thankfully I only live 5 minutes from my RE) and the baby was fine, perfectly on track at 8w4d. My RE stated he felt it was a clot leftover in my cervix released by changes in my progesterone. My first progesterone level was 20 (which is considered "low" by my RE after IVF) and had to add prometrium tablets in addition to my PIO injections. I was taken off the PIO injections last week after a progesterone level of 48. Has anyone else ever had this occur?