Property under construction

I have purchased a property in ambarnath, in thane, maharashtra. as per agreement and also verbal promise, the property was suppose to be handed over to me by dec 2016. now till date only 6th slab is completed (total 7 floor) and work is halted since last six month. even in 2016 also work was stoped for almost 9 months, later they started completed till 6th slab and now again worked total stand still. my all communication with them including personal visit results only in vague replies and no concrete confirmation. now they say that property will be handed over in may 2018. i no more trust their words, as work can get completed only when something moves. there is not a single worker at site since last may months. i have already paid almost Rs. 30 lac through my banker including my contribution and property registration charges. i am paying interest on all the money disbursed by my banker to builder. i am forced to pay for the negligence, carelessness and casual approach of builder. kindly advise, is it possible to force builder to pay the interest??? or buys back the property and pays me back the entire amount paid till date?? Kindly advise an appropriate action so that i can come out of this mess???