Ideally, your first OB appointment falls between 6 and 10 weeks of pregnancy: before that there is still little to see on ultrasound, and later you delay important tests. Some situations call for an earlier appointment, by 6 weeks, including a previous ectopic pregnancy, bleeding or pain after the positive, and pregnancy through assisted reproduction.
Booking the appointment is on the book's checklist for the first 24 hours after the positive, aiming for an appointment by 8 weeks. Remember that weeks are counted from your last period: on the day your period was due you are already about 4 weeks pregnant, so the ideal window is only 2 to 6 weeks away.
The window has a reason. At 6 weeks or more, a transvaginal ultrasound can show the embryo and the heartbeat. Earlier, there is little to see. Later, you delay the first-trimester tests that the OB orders at this visit.
Bleeding or pain moves the appointment earlier, but some signs cannot wait for any appointment. Heavy bleeding (more than one pad per hour), severe abdominal pain, especially on one side, shoulder pain with any bleeding, or dizziness, pallor or fainting: go straight to the emergency room.
This is the start of a relationship that will last 9 months, maybe longer. There is no "best doctor for everyone", but there are criteria that help.
Your first OB appointment is Chapter 39 of Map to the Positive, in Station V (Positive), which also lists the documents to bring and the first-trimester tests. Because the book starts long before the positive, much of what the OB will ask for may already be in your hands: the 11 preconception tests from Station I and your cycle charts from Station II. It is useful to keep for these weeks, or to give to someone who is still trying.
Take 30 days. If it does not give you more clarity than everything you have read for free so far, ask for a refund and you get every cent back. We cannot promise you a pregnancy. We can promise you will not be guessing.