Nervous or just overthinking

In July 2011 I miscarried after a blight ovum and stopped trying cause of my fear of having another miscarriage but last week Tuesday I went to the doctor and found out that I was 8 weeks along.. I had an ultrasound and the doctor said everything looks great heartbeat and all.. Fast forward to now every min I'm thinking something is wrong with the baby or that I'm going to go in for my next app and I'm not gonna see my baby or a heartbeat..the next time I actually will see my baby is when I go in for my fetal nucheal translucency in 2 weeks.... Am I just worrying too much or is this normal