How to file a complaint against builder for not giving possession

I had booked a flat at a renowned builder in the NCR. The agreement was signed more than a year after booking and paying a huge amount of money. The plans of the project were approved more than six months after payment of first /initial booking amount of Rs.15 lacs and another about 50+ lacs during these six months (Before approval of the building plans). I was forced to sign the Builder Buyer agreement as per the builder's drafting, failing which I was threatened to lose all my money paid till then, which was almost Rs. 96 lacs. The first payment was made in Feb.2013. The building plans were approved in Sept.13.the possession was supposed to be handed over within 42 months as per the agreement.Forty eight months have since elapsed, but the possession is no where near. I have already paid more than 1.5 Crore, major portion of which is a housing loan. The payment of heavy EMIs have already started. I have made objections to major changes in the building plans by the builder.