We suggest that you should register a complaint of Bigamy under Section 494 of the Indian Penal Code against your husband in the nearest Police Station. In the recent Supreme Court Judgement, it has been held that proof of first marriage is not required at the time of registering of FIR. It is incumbent upon the police to register the FIR and it is for the trial court to decide the veracity of the allegations.
However once the matter reaches the Trial Court, you will have to adduce evidence to prove the existence of your marriage.
In case of religious marriages the Priests who solemnized these marriages, the performance of all valid rites & ceremonies required for a valid marriage, witnesses to these rites & ceremonies, the accused had a living spouse at the time of second marriage or the first marriage was not dissolved by the decree of dissolution by a competent court, all these form necessary piece of evidence.
In case either of the marriages is not religious marriage but civil marriage than the complete record of the marriage have to be summoned from the office of the Marriage Officer/Registrar along with the Marriage Officer/Registrar to prove the charges of valid civil marriage being performed by such person.
As you have suggested that you do not have conclusive evidence as the your marriage, then we shall have to adduce circumstantial evidence to prove the existence of the marriage.
And we would like to mention that there is no limitation period for lodging the said complaint.