Consumer Redressal

Sir , i purchased a 1 bhk flat at mira rosd , thane measuring 770 sqft. The builder gave me date of possession 15/05/14, but till date he hasn\'t given possession . now the thing is that i have to spent money 15000 as rent where i am cureently living plus i am in deep mental agony.Builder says that noone can harm him as he has mentioned in a clause that possession is subject to occupation certificate.I fail to understand that why a consumer should suffer due to such clauses which a builder puts for his own safety. this dosent means that if the builder fails to obtain occupation certificate then poor consumer should suffer. Builder pressurise to sign that document or else take back amount after deducting 20% of the amount.Hence poor consumer is left with noway other than to sign that document. Moreover i was promised to get 770sqft of glat but the builder gave me only 720 sqft less 50 sqft.Please advice me . Thanks