Delay in providing possession of flats

Hello, I have booked a flat in June 2012 in Ghaziabad when it has not even started construction. At the time of booking i was told that construction is about to start in next month but it took ages to get the excavation done. In the current status, where i have already given 70% of the amount, the construction of 5th floor slab has just completed. With the current status and progress of construction, it doesn't look possible to me that the possession can be given in next 2 years. In my agreement document with builder, (which i have received 2 years back) they have put 2.5 years + 6 months (grace period) after which they are liable to pay penalty to me @ rate of Rs 5 per square feet. As i don't see the possession sooner and already paid a big amount of my hard earned money, I am seeking your advice what best can be done in this situation and how can i tighten my knot to builder so that i don't have to pay anything further until it is close to possession. In case of any further delay, how can we recover my loss that has happened due to builder?