How long is your period on progesterone?

So I took the first round of progesterone pills for 12 days from the 1st to the 12th like my Dr told me to. I started spoting on the 8th and then started to bleed the 9th and I haven't stopped since. Its not a heavy period but dang at the cramps! My periods are usually over by now, but ive got no signs of it slowing down. I did have a period last month and every other month for a while before hand also. I'm not undertanding all this, should it be this long and painful?