12 weeks tomorrow! still paranoid...help

we will be 12 weeks tomorrow. We had an ultrasound at 8.5 weeks and saw a nice strong heart beat, baby is measuring almost exactly size for date, 2 arms, 2 legs, etc. doctor said baby looks very healthy and im suffering from hyperemesis gravidum. My mom miscarried a baby at 12 weeks in the early 90s. she found out at her 1st ultrasound at 12 weeks the baby had no heartbeat. she never bled and never had any symptoms of miscarriage and had to have a d&c.; im scared. could this happen to me too? could I feeling super pregnant and then when I go for my next ultrasound, the baby not be ok????