Fetal arrhythmia/irregular heart beat. Should I worry?

Al

Went for an ultrasound today and my baby’s heart looked normal they said, but slight arrhythmia. HB was 139 but there was a little flicker every 5 or 6 beats or so. Although the doctor said he wasn’t too concerned, he wants me to come back in 2 weeks just to check again. So obviously I’m very scared and I can’t stop thinking about it. Anyone else ever have this happen? And if so, what was the outcome? I’m almost 24 weeks