Question Summary:
Does reverting to Islam nullify ones christian marriage? Or was it never valid?

Question Detail:

Hello, I am a convert. I was married in a Christian ceremony before my conversion. I have since separated from my husband 8 months ago. Do I have to take any steps to be considered divorced islamically? We are getting a legal divorce. Or was the marriage never valid in terms of Islam ? I am asking so I know whether I am free to do Nikkah if I meet the right person.

Answer :

 
Sister-in-Islam
It is pleasing to note that Allah guided you to the ultimate truth – the religion of Islam. May Allah keep you firm and steadfast on Islam. Aameen.
Your marriage according to the Christian ceremony was valid. [i] When you reverted to Islam and your husband refused to revert with you, you had to separate from him and undergo a waiting period (iddat) of three menstrual cycles if you experience menses or three months if you don’t experience menses.[ii] Upon the expiry of the iddat period, your marriage with your non-Muslim husband terminates and you are free to remarry. If you had already completed the iddat as explained above in the past eight months, then you are free to remarry.
And Allah Ta’āla Knows Best
Aboobakr Siddeeq bin Mufti Amjad Mohammad
Student Darul Iftaa 
Azaadville, JHB, South Africa 
Checked and Approved by,
Mufti Ebrahim Desai.