according to your description I am thinking that you estimated your pregnancy
to be of 10 weeks but it is actually of 6 weeks only.
if not when the heart beat stopped at 6 weeks then why you waited for 4 weeks?
anyhow medicines to induce abortion
are prescribed usually up to 7 weeks of pregnancy only.
usually after completing the tablets within 12 hours you will start bleeding and in around 48 hours abortion will be completed.
you may have abdominal pain
and some amount of nausea
during abortion, in case of excessive blood loss giddiness can occur,
better take rest during this period.
after completion of abortion consult doctor
and undergo checkup to find out whether it was complete abortion or not.