I don't think anything decreases chances of miscarriage like that but DO take a prenatal vitamin. They sell those OTC if you don't have a prescription. Congratulations! It seems very early to get a positive test though! When is your period actually due? Did you use a first response test? The test was read correctly, right? You didn't leave it sit or anything like that?
A_joines, I hope it all works out for you, but as SpecialMom said, this is really early for a test to be detected. I think you should brace yourself for the possibility that the Early Response Test picked up your previous pregnancy, with the HCG not quite being completely out of your system.
To go from a very early miscarriage, to pregnant and testing positive again in the space of 3 weeks is unusual.
I do wish you well, and know that if you aren't pregnant again, chances are high that it will happen for you at some point soon.
Hope you post back with the results - best wishes!!
Thinking of you today, A. Hope you're doing ok.