[RCF]

After the second time, his uncle saw Nikitha buying birth control pills at the medical shop and Sudagaran mentions the same in front of Jay about how people think. Wouldn't that give Jay insight that Nikitha is sleeping regularly with Tarun? He might not know exactly how many times but she buying the pills will be only for having sex with Tarun only no?

Jay is broken down because of various reasons not because he didn't know about their sex before, he knows they were sexually active even before his uncle says she bought pills. 

He is broken down watching Nikita in the act of sex...the sheer intense sex she was having free of guilt, pleasure and pain coursing through her and desperately trying to please Tharun while taking the pain...the intimacy broke Jay. 

What broke him was the fact, the truth that he was forcibly pushing outside his mind all this time and ignoring Nikita's words all this time that she has moved on....That truth is now shoved into his brain cells permanently whether he agrees or not, he came face to face with that fact that Nikita was right, she has moved on from him in real, the sheer guilt less sex and her aliveness in that moment pushed Jay into darkness which showed him the truth of what he had put her through with Anjali's episode, that broke him....

He now knows the pain she went through at that time...this is his ultimate moment of realization that he himself lost her by his own actions and denying that fact forever would not get him anything in return and in turn shows him that he has to let her go now and move on...that realization broke him....

You will see new Jay now....

~RCF