No, it's nothing you did, but sometimes your body just doesn't produce enough, the cause of that might not be easily found for it. I start progesterone injections this week to keep the risk of preterm labor down.
No, it's nothing you did. Some of us just don't produce enough of it. I've been on a progesterone suppository since I was 4 weeks. This is my last week on it. At 12 weeks, the placenta takes over progesterone production.
ETA: My first pregnancy was fine, then I had 3 miscarriages caused by low progesterone and a clotting disorder.