I'm sorry but Your rank could not be predicted as there are certain factors you need to understand. Factors like what will be the difficulty of paper? If you are writing your entrance exam with pressure then you wouldn't be able to do well. If you are relaxed and then you write the paper , you would do better in exam. 

AIIMS 2019 will take place in May 2019. So you have some months with you. Is it too late?Well it depends upon whether your concepts are clear or not. Remember one thing :- Practice, Practice and Practice. Only Practice will help you achieve high. 

If you still have any queries feel free to ask in the comment section down below.

All the best.