I was taking progesterone with this pregnancy (I also did with DD).
I don't remember when I stopped with DD, I think around 12 weeks. I was supposed to be on it the whole first trimester, but I just couldn't take it any more.
I see a midwife group for prenatal care. One wrote me the prescription for progesterone, and told me that most providers recommend taking it through week 10 but she felt more comfortable with week 11. I had a prenatal visit at 10 weeks 5 days with another midwife, who said to stay on it until 12-13 weeks. When I asked her why she thought 12-13 when the other midwife said 10-11, she told me that they aren't really sure how long to recommend it so some providers recommend to stay on the whole first trimester just in case. My prescription was going to run out when I was about 11.5 weeks, and she told me to just finish it but that I didn't need to get a new prescription to continue longer, unless I wanted to.