Nak, I'm so sorry you're going through this, that's such a heavy thing to carry right now. Please follow your OB's advice closely and go back for that repeat ultrasound, okay? They know your situation best.
Honestly, a few of us moms have been through similar scares, and what helped was leaning on family and close friends, don't try to feel okay alone. One of my friends said talking to her OB about what to expect next helped her feel less scared of the unknown. This is medical and emotional, so please don't hesitate to reach out to your doctor if you need support, or even consider talking to a counselor if the waiting period gets too heavy for you.
Sending you so much love, mommy. You're not alone in this.