Progesterone supplements are controversial. For some women they seem helpful. For others, they are not. However, the evidence suggests that they may only prolong a non-viable pregnancy. Doctors are sometimes pressured by patients to be given progesterone. Other doctors may recommend them. There is still A LOT with regards to pregnancy that is not well understood yet and I think there is not a great evidence for or against them, which is why some prescribe progesterone and others do not. With your hCG being what it is, I wouldn't worry too much as long as it keeps rising well. Keep in mind that between 1,200 and 6,000 mIU/ml, it can take 72-96 hours to double and after 6,000 mIU/ml, it can take up to 4 days to do so.
It sounds like everything is going well. Good luck and keep us posted.