High hcg levels but only gestational and yolk sac seen

So I went to urgent care for some spotting, they said my hcg levels are very high, but when they did an ultrasound only a gestational sac and yolk sac were seen. I got a positive early on like a week and a halfish before my missed period. Has this happened to anyone else? According to the sac I’m around 4-5 weeks.