8 weeks couldn't see anything in sac + red medium spotting

I went to the doc yesterday because I had some red spotting, it is heavier today. I had an internal ultrasound, and there was nothing to be seen in the yolk sac. They told me I have a threatened miscarriage and I will go back for a repeat ultrasound next week. My levels are at 16,665 and cervix is closed. I'm hoping nothing happens to the poor little jelly bean :(