When to take progesterone?

My fertility doctor said as soon as I get a positive pregnancy test, she will put me on vaginal progesterone since I’ve had 3 chemical pregnancies However I’ve heard of people using progesterone as soon as after ovulation so I asked her if this would be more effective. She said if you’re not careful when you take it after ovulation then you can actually disrupt the process and inhibit ovulation I guess? so she only prescribes it once pregnancy is confirmed.

Looking for more advice opinion.. I’m thinking of getting a progesterone cream to start using a couple days after ovulation. What’s your experience with progesterone?