Is it possible that people miscarry and do not discover this until their 12 week dating scan?

I'm petrified of having miscarried again! I have been so anxious since 5 weeks - when I found out I was pregnant. I had a "missed miscarriage" last year so didn't start bleeding until week 10, although I'd lost the baby around 5-6 weeks. I had a scan at 7 weeks this time and we saw the flicker of a heart beat. I am now 11.5 weeks but am so terrified of going to my dating scan next week only to discover I may have miscarried again. I felt pregnant immediately in my last pregnancy, had nausea, sore etc right upto week 9. This time the only pregnancy symptoms I've had are swollen s and tiredness. Is it possible to have miscarried only I not know about it yet?