Usually when trans abdominal scan is taken fetal pole
may not be detected by 5th week.
And some amount of spotting is common in early pregnancy
due to causes like,
while getting embedded in uterus
wall can damage some blood vessels leading to spotting.
-Bleeding may be seen on expected day of periods even in pregnancy.
-Increased blood supply to local organs can cause spotting even on mild friction.
So you wait for two more weeks and undergo repeat ultrasound
which will possibly detect the fetal pole.
But if the bleeding becomes severe or pain abdomen etc appears better to consult gynecologist early.