Well, you might not. But I would see the doctor on Tuesday. If you are pregnant, you certainly don't want to lose it for not having progesterone -- it's given as a matter of course in early pregnancy in Europe (in other words, is not considered dangerous at all). But at least get a blood pregnancy test to see what might be going on.
Do you know any reason for your miscarriages? (For example, some women take progesterone immediately if they think they are pregnant, in order to hold the baby.) Your spotting could be the (near mythical) "implantation bleeding," meaning an embryo has dug in and is beginning to grow. Or, it could almost as easily be breakthrough bleeding. See the doctor and get a blood pregnancy test and if you are pregnant, ask about progesterone supplementation until week 12.