Worried

This is my 4th pregnancy.
I've miscarried 2 previous times. I had one full term baby girl who is now 6 years old. I'm worried that this is another miscarry due to the fact I feel totally normal. I have absolutely no symptoms of being pregnant. 
The only proof I have is a late period (it's been over a month) and a positive test. I have an appointment in a week, and then I get to schedule an ultra sound. 
So basically I'm playing the waiting game. 
My last misscarriage was this exact time last year. I had an ultrasound and the heartbeat was low (like really low) I went back a week later and the heart beat had stopped completely. 
I'm scared. I don't want to see another flatline...