the doctor should have said smth, even if is ectopic pregnancy. or it could be ur 8 weeks is miscalculated as ur ovulation could be much later. u can also request for a hcg blood test to see if the number is high enuf. the number should double every 2 days to have a viable pregnancy. or worst case scenario is u detected the pregnancy early but u only get to scan now at 8 weeks but it's a biochemical pregnancy so u dun see anything. soon u will have menstrual blood flowing.
try to get a second opinion, can try to do a vaginal scan which will be more accurate instead of ultrasound on tummy cos sometimes the detection not strong.
What did the doc say? By week 8 should detect heartbeat and a small fetus. Might be ectopic?
Don't scare and stress yourself first. Will be good to seek for second opinion..
Try for second opinion?