I have personally witnessed a person who was in the same situation as you. After exhausting 4 years of his life, he was unsure whether he should give NEET for the fifth time. Till now he was not a sincere student, but in his fifth attempt, he took thigs seriously and finally got a government medical college.

So, if you are completely sure that you would give your 100% this time, only then go for the fourth drop! If you are even a bit unsure, go for your different line. In any case I wish you all the best and hope you give your 100% efforts.