when should I make a obgyn appt

Jess • Mommy of 2 💜💙 with 12 years of LOVE 👨‍👩‍👧‍👦 after 7 years since our last baby we are Happy too announce Baby #3 is another BOY! 36weeks.

Newly found out I'm expecting #3 .. roughly 4 weeks along . when should I call and make the ob appt????