Answer
Wa `alaykum as-salamu wa rahmatullahi wa barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- A new Muslim should keep good relations with his or her family. Islam calls for good ties with all people.
2- Though a wife may bear her husband’s last name, she should keep her biological father’s name. Islam doesn’t change people’s lineages.
Responding to your question, Sheikh Kifah Mustapha, the Imam and Director of The Prayer Center of Orland Park and representative for Dar El Fatwa of Lebanon in the US, states:
It should be known that even if people convert to Islam, this should not cancel their line of family. Allah Almighty says: “Call them by the names of their fathers. This is the right course in the sight of God.” (Al-Ahzab 33:5)
For such, I am not in favor of changing family names of wives to their husbands. Now in some cases, it might be a necessity for immigration papers or such.
If that is the case, I can see that only the last name of the husband is added at the end to the wife’s last name keeping her maiden name too.
In your case, I see that you only changed the last name. If you did keep her middle and last name but just added yours, it should be fine.
Allah Almighty knows best.