First timer

Soooo I took a test 5 days before my missed period and got an extremely faint positive, I took another yesterday (1 day before my missed period) and it was much darker! Hoping that means my levels are rising nicely-I am super nervous because my family has a history of miscarriage. The app tells me my due date is May 20, 2019! I am calling my dr tomorrow to see about a blood test. How long does that take? Would love to hear any thoughts!