My ex took me to court about 10 years ago for visitation. We are back in court again but his lawyer is the magistrate who ruled on the original custody/visitation case. Is this a conflict of interest? I
Yes it is. You should: 1) find your own attorney, 2) inform your own attorney about this conflict so they can file a motion to disqualify opposing counsel. If your opposing counsel knew of the conflict and concealed it, then it could become a bar complaint.
FInd an experienced domestic relations attorney immediately to handle this litigation.