wa'alaikum as'salaam,
You mentioned that first time you went in state of irham to do umrah. You might want to check the two rulings below similar to your situation and also consult a scholar on this matter.
She entered ihraam for ‘umrah, then she decided not to do it. What does she have to do? .
She entered ihraam for ‘umrah but was afraid of the locusts in the haram so she did not complete it
Is ‘Umrah obligatory or Sunnah?.
The correct one of the two scholarly views is that ‘Umrah is obligatory, because Allaah says (interpretation of the meaning):
“And perform properly (i.e. all the ceremonies according to the ways of Prophet Muhammad), the Hajj and ‘Umrah (i.e. the pilgrimage to Makkah) for Allaah” [al-Baqarah 2:196]
http://islamqa.com/en/ref/39524
But is it wajib (obligatory) everytime you visit makkah?
I have not read or come across anything of such.
There is such a thing as Tawaaf al-qudoom (tawaaf of arrival) for Hajj. This is done by the pilgrim who has entered ihraam for Hajj and by the pilgrim who is doing Qiraan, i.e., joining ‘Umrah and Hajj, when he reaches the Ka’bah. I"m not sure if there is a similar thing also for those arriving into makkah. I do recall reading something similiar to it, not sure if it was just some dua you recite when you entered makkah or do the tawaf as well like you do 2 rakah sunnah'ul salam when you enter any masjid. Might want to check up on that, maybe someone here came across such reading also.