First trimester

Hi everyone,

This is my second pregnancy. I had my son 15 years ago so it feels like I'm pregnant for the first time! I am about 3 to 4 weeks along, gynea says it's too early to tell and I'm due for my next check up in 4 weeks. When my doc calculated my pregnancy using my last menses he came up with 7 weeks so now I'm stressing cos he says it could be the conception date is wrong or maybe the foetus isn't developing as it should. Anybody else experienced this? I know there isn't a sure way of knowing when conception took place so maybe I'm being silly?