Hello there.

The last date of submission of application form of NEET UG was December 7, 2018, and the last date for successful payment was December 8, 2018. The examination is scheduled to be conducted on May 5, 2019.

It's been long since the dates got over and as the dates have passed there is nothing you can do now. As far as my knowledge goes, there is no provision of submitting the form or completing the steps of the application after the dates get over. You would only be able to apply for the examination of 2020 now. Start studying hard for clearing the exam in the 2020 attempt itself as you have already wasted one year. 

I don't know your personal problems but truly, it is the responisbility of the candidate to be upated with the schedule of the examniantion and to stay updated with the latest information by regularly checking the official websites of the examination. This is pure negligence on your part and is surely very unlucky and upsetting but there is no way out right now. Target NEET 2020 and come out victorious. 

All the best.