1)non registration does not affect validity of marriage
2) if marriage is not registered wedding invitation cards , wedding photographs are sufficient to prove that marriage has taken place
3) mere wedding invitation cards is not sufficent to prove the marriage
4) Section 7 of the Hindu Marriage Act says that (1) a Hindu marriage may be solemnized in accordance with the customary rites and ceremonies of either party thereto; and (2) where such rites and ceremonies include the Saptapadi (that is, the taking of seven steps by the bridegroom and the bride jointly before the sacred fire), the marriage becomes complete and binding when the seventh step is taken.
3) you can examine witnesses present at time of marriage to prove that marriage was solemnised with your husband