6w3d preg since lmp,scan show gastro sac but no yolk sac,what does that mean?etopic pregnancy? scared!

Gestational sac?: do you mean gestational sac instead of Gastro sac? at 6+3 wks I would expect to see an embryo with a heartbeat. since this is not the case the pregnancy is either not as far along or, worst-case scenario, it is a blighted ovum. this is just a stational sac without an embryo in it. unfortunately this pregnancy would end in a miscarriage. another ultrasound in a weeks time will provide an answer.