Hello Aspirant, 

Don't worry regarding that.  As each year number of seats in NITs and IITs increase. And that's the reason why a person with your rank in 2017 was not getting and in 2018 it was available. 

Feel assured regarding that, this year too the cutoff will be almost around or might be more beneficial then previous one's. 

Hope this will help. 

All the best for future.