Dear S.P.,
If the first marriage is valid and it was solemnied in accordance with the procedure prescribed by law (and this marriage also was registered and had registration certificate), then your marriage was a second marriage and it is void. If you want to severe this marriage relationship, then you have to file a petition under Section 11 of Hindu Marriage Act seeking the marriage as null and void as it violates Section 5(1) of the Act. It is not divorce. The null and void marriages cannot be dissolved by decree of divorce. After order is passed declaring your marriage as null and void, you are put in the same position as you were earlier to the marriage and is entitled to go for another marriage legally. For proving your marriage void, you have to produce his first marriage certificate or sufficient oral evidence to prove that marriage and also have to produce your marriage certificate. It is civil remedy.
In addition to this, if you feel you are cheated, you can file appropriate police complant and can pursue criminal case against him.
Your petition under Hindu Marriage Act can be filed eitther from the place where your marriage was solemnized or where you both resided together in matrimonial relationship or where he resides and finally where you reside at the time of filing the petition (if you are in India).
Hope, I clarified all the doubts. I reiterate the remedy what you should seek is "dissolving the marriage by the decree of nullity" under Section 11 and NOT DIVORCE DECREE under Section 13 of the Act.
Warm Regards,