I had my first scana t 11 weeks but that is because I chose to have the NT scan to check for down syndrome, trisomy 18...etc....if I hadn't had that it would have been my 18 week scan.
It is usually 12 weeks. I had early scans with my first two pregnancies (both of my boys were fine) and with this pregnancy. I have never heard of an u/s causing problems. I wouldn't let it worry you. I doubt very much in those cases that it was the early u/s that was the cause.
normally 12 weeks your first ultrasound is, then 20 weeks, but it depends when you go the doctors and say you're pregnant, i didn't know i was pregnant with my 1st boy til i was 23 weeks 6 days gone and that was when i found out at first scan, then i had another scan at 28 weeks, how far pregnant do you think you are? you don't have to have the scan you know, when i had my second scan at 20 weeks i thought it was painful at one side because when she pressed on my stomach it really hurt, good luck with the pregnancy