It's perfectly normal to be worrying, especially at this point. I'm almost 16 weeks and I still worry sometimes that something will happen to this pregnancy. I think it's harder for women with medical conditions because they lose their innocence about pregnancy long before they actually conceive. It's so much harder when you know the odds of something going wrong from the very beginning.
That being said, more than likely everything will go fine with your pregnancy. I think getting the progesterone checked is an excellent idea since it's vital to supporting a pregnancy. I would also suggest pushing for an early ultrasound if you can so that you know things are off to a good start. That went a long way toward easing my mind.
For now I would say take a deep breath and do your best to just enjoy being pregnant, and know we're here if you need us.