Can I give jee main exam in 2019? If last time I given jee main exam in 2017 with 12th board. But I am not giving jee main exam in 2018.

According to jee mains 2018

Only those candidates who have passed their Class 12th Exam or any equivalent qualifying examination in 2016 or 2017; or those who are appearing in their Class 12th Exam or any equivalent qualifying examination in 2018 are eligible to appear in JEE(Main)- 2018. Candidates who passed Class 12th/Qualifying examination in 2015 or before as well as those who will appear in such examination in 2019 or later are not eligible to appear in JEE (Main) – 2018. Candidates who appeared in class 12th/equivalent qualifying Examinations in 2015, did not pass in 2015, but passed in 2016 are also not eligible to appear in JEE (Main) 2018.

Yes u can give in 2019 as apperaing with another board

You can attempt at JEE Mains three times.Oncewhile appearing for your 12th board or other qualifying exam and two more times after passing 12th or the qualifying exam. But do note that the 2 attempts need to be in consecutive years right after your 12th.
So soryy friend you cant give now in 2019 as you had a break in between.