Welcome to Healthcaremagic.
If the Urine pregnancy
test was done and it showed positive then the pregnancy is strongly considered.
In gestation of 5 to 6 weeks a gestation sac is seen in the scan not the baby.The measurements during that time are always not universal.Hence, I would ask you to be patient and get a scan at around 7 the week where fetal heart can be visualised by the ultrasound
Wish you the best.