Waleikum Asalaam,
You'd have to ask a sheikh to be honest, but from my understanding, if both parties do it mutually through secular court and the intention of divorce is there, then it is valid. I did my divorce through secular court also and we also lived separately for almost 6 months prior to that, so my case is slightly different to yours. My now husband also did his divorce through secular court as his ex-wife didn't want to involve a sheikh, and several sheikhs have told him it would be valid this way. Allahu alim.
Please ask a qualified person sis, it is better to be on the safe side insha'Allah.