My daughter was told at her first scan that she was almost 2 weeks less pregnant than her dates said,she went for her 20 week scan a few weeks ago and they told her she was 1 week behind dates,her midwife says her measurements make her almost exactly on dates. I had the same with my son 10 years ago,at 12 weeks they told me I was 9 weeks which was an impossibility as I knew exactly when I had concieved.lol.By my dates he was due August 7th,by their dates he was due September 3rd,he was actually born on August 23rd and his skin was peeling,this only happens with late babies,so my dates were the correct ones. Scans are not always right so don't think that what they told you is set in stone.
Like redcrx said,getting to 10 weeks is a good sign,I have read that most miscarriages occur around the 8 weeks stage or before so try not to worry too much.Many women go on to have normal pregnancies after suffering a miscarriage so the fact that you had one last year doesn't increase your chances of having another really.All pregnant women worry about miscarrying so your fears are perfectly normal.