IUI & Prometrium

I had my first IUI on March 15, with a progesterone check a week after. They prescribed me Prometrium vaginal

Suppositories to take until Monday the 29th, where I take an at home test. I was advised if the test is negative, to stop the Prometrium. If positive call the clinic for hcg blood test.

My question is-

1.anyone who has taken Prometrium, did it delay your period and by how long?

2. What concerns me is taking a test 2 weeks and 2 days past my IUI and not having enough hormones in my body yet to show on a pregnancy test, stop the Prometrium and find out I got a false negative. Has this situation happened to anyone?