Miscarriage - ???

On May 18th, I got my first ultrasound (picture) the tech believed I was only 4 weeks. She made everything seem like it was good and so far so good. Then I went back on the 24th and she looked and said I would have a miscarriage. Something about the sac was laying long ways? Something in me says she didn't look enough. She kinda went for one spot and stayed on it. She didn't look around much. But she was a tech and I'm taking her word for it.

When will the miscarriage happen? I have no cramping, no spotting. No pregnancy symptoms either really. Will it be soon? What should I expect and prepare for?

She said they could do a D&C but I'm holding out.

Thanks for any advice or inputs.