My ex-husband and I worked with the same attorney on my first divorce. He acted as attorney for bothof us. Can he now represent my current spouse ?

Technically the lawyer can do this because it is a different case than the one between you and your prior spouse.  It's not an actual conflict, but it is pretty frowned upon to file a suit against a former client.  But the very fact that you say he represented both of you in the first divorce indicates that this attorney is playing fast and loose with the rules of ethics.  He could not have represented both of you as your lawyer.  He could only have acted as a mediator, if he is qualified to do so.  I think it is more likely that he actually represented your ex-husband and considered you the adverse party, but failed to make that clear to you.  Lawyers can get in a lot of trouble for that.  He should have made it clear which one of you he was representing and he could not provide legal advice to the other.