Talk to your parents. Show them this Times ranking of top tech and engineering schools in the World:
Purdue is ranked #45 in the world, ahead of all the Ivies except Princeton, Cornell and barely behind Columbia. Yes it’s ahead of Harvard and Yale! Don’t worry you won’t have any problem getting a job with a 3.5 in CS from Purdue, it’s a well known engineering school across the country. Tell them you are happy and doing well there, and that will only help with your grades.