Hi,
I am not sure why you had a miscarriage. Placenta previa is a common problem during pregnancy. I have heard that if you had a placenta previa in one pregnancy then you have a higher chance of having it in subsequent pregnancies. But that should not deter you from having a baby seeing that's what you really want. I would talk to your ob/gyn about your medical issues and then come up with a plan.
Hello, Unfortunately, the only way to check if you are pregnant is by a HPT or blood test. The brown discharge could be implantation bleeding. I would wait a couple of days and do a HPT at home to check.