Hi, welcome to HCM.
At four weeks gestational sac
can be seen but yolk sac
and foetal pole will seen clearly at 6 weeks only.
As you had heavy blleding and clot . The possibility of incomplete abortion
could not be ruled out.
You gynaecologist advise is correct. You need to do follow up scan . It a quite anxious situation but there is no other option. Be patience and don't get anxious.
Hope I have answered your query.