Hcg not doubling, Ultrasound at 6 weeks

Wondering if there's anyone else out there who is going through or has gone through the same thing.

-6 weeks pregnant

-frequent light spotting

-light cramps

-Hgc levels slowly rising but not doubling

Doctor is suggesting an early ultra sound tomorrow. I'm worried it may just make me more anxious if we don't see a heartbeat. But at 6 weeks we may not see much anyway, right?

Anybody have stories about early ultrasounds at 6 weeks? What are we supposed to see? I just don't want to think the worst if we don't see anything.

Thanks!