What I have been told is that progesterone can help support a pregnancy, but it won't stop your body from miscarrying. If it is going to happen, then p4 won't stop it from happening. At least that's what my former RE told me. I completely understand where you're coming from. Having had three early losses myself, the early days are really difficult. Maybe having the b/w will help to ease some of the anxiety. Wishing you all the best.