Went to my ob today and he did an ultrasound and for 4.5 weeks we didn't see anythig?! is that bad? i thought u c a gestational sac at this stage?

Early OB ultrasound: With standard transabdominal ultrasound, radiologists can see a gestational sac around the 5-6 week mark. Before the 5-6 week mark, it's not unusual to not see a sac or fetal pole. If nothing is seen, this could mean a couple of things. Most likely a very early pregnancy (with positive beta hcg). The thing to do is consult ob, followup serial beta hcg, and followup OB ultrasound in 2-3 weeks.