No active, pulsating fetal pole at 8weeks

[Kofosh]

Good Morning..this is my first pregnancy and I'm 8weeks gone. .went for an ultrasound yesterday because I was feeling cramps at my pelvic area..the result of the scan I did was no active, pulsating fetal seen....he later said its either a threatened abortion or luteal cyst....I was advised to rest for 2weeks then go back for another ultrasound. ..I'm worried ...is it normal not to hear the heartbeats? Pls I need your advice.  Thanks so much