5 weeks 4 days spotting- help

Over the last week and a half I've had three instances of spotting with a small amount of streaky red blood. I had an ultrasound Wednesday, but the spotting didn't concern the doctor. Too early for a heartbeat. He didn't order tests for hcg levels because he wasn't worried. But I'm worried. I had a miscarriage in April. It isn't bleeding, just spotting, and I only have the mild, normal growing cramps. My next ultrasound is Saturday and I feel like I'm going to burst, waiting that long. Any encouragement? Or honestly, does it not look good for this baby?