6 weeks spot on is a bit too early.
I had a us at 6+6 very similar and they made me come back in two weeks just to make sure.
Mine didn't end well but I did a ton of research so i remember reading 6 weeks is a bit too early.
There can be variablity with ovulation, conception and implantation.
At 6 weeks its about 3mm and i think grows 1mm a day, if you were off by 3 days it might only be 1mm.
There are many stories on the internet of things going both ways.
it is way too early to give up hope.
As for 9 weeks by LMP, but 6 weeks by u/s measurements, you absolutely could have had delayed ovulation due to stress, travel (if I fly during AF, my ovulation will be delayed by two weeks), illness, etc. And some people don't have 28-30 day cycles to begin with, and ovulation is usually around 14 days before AF, so that can make a big difference in pregnancy dating as well.
As for what your u/s means, unfortunately there's no way to tell from just this one scan, or even from a scan plus quantitative HCG test. The only way to know if the pregnancy is progressing normally is to go in for a repeat u/s a week or so from the first scan to see if the expected growth has taken place. Please don't let a doctor convince you of anything without a repeat u/s!
Sending you positive thoughts for a healthy, sticky bean.