Not having Evidence of Marriage

You have to do three things :-

1. Change your advocate. 

2. If the registrar is saying that you will not having the sufficient proof then tell him that what he want to file the suit. Even after having sufficient proof he will not register your case then directly go to the judge and tell them to advice in this regards. 

3. If judge refuses for the same then file a appeal to the appellate court. 

If your husband is employed or if there is any ration card or bank account or AADHAR CARD seek such certified copy of such document that stated that you are the wife of so and so as per public records. Recollect all those past incidents to find those records/photographs that may help you. (This is in addition to what Shri MJ has replied and his guidance is proper, but these Registry persons harass you more in regular proceedings if You comment on them)

Hello, Mr. Ritesh

In this famous case Vanajakshamma And Ors. vs P. Gopala Krishna, The learned Counsel has relied on in support of his contention that a Hindu marriage need not take place in the presence of a priest, and the tying of a 'Mangalsutra' in the presence of an idol is also one of the forms of a marriage known to Hindu Law. 

You have to notice three things :-

1. You have to collect any possible documents for the proof of marriage like, photos of the time of marriage, any thing which proves that they are married, any person who saw that marriage etc. 

2. Secondly, Try to gather some information from mobile phones, photos, videos of any tour or they visited any place together. 

3. Thirdly, you are saying that you don't have any proof to prove the marriage then why are you wanting the divorce. It is already invalid if both the parties not having any proof.