9w but only 6w?

Adelaide • Addy*
My lmp & hpt say I'm 9w but ultrasound said I'm only 6w? Had problems seeing baby last time, could only see a sac no baby, so going up for 2nd ultrasound in 10-24days. 
I started losing symptoms as well, started spotting, they said there's a 50/50 chance I'm having miscarriage but the baby just might be growing very very slowly. Any advice or similar stories?