I think he isn't used to saying stuff like to anyone
He is having hard time with it
When he says he trust someone he means it.
i think he is starting to think that maybe prerna has started to understand him little as well but when she question/accuse him.
He is hurt that she doesn't trust his words that he won't disrespect her or hurt in anyway
Like i said he should be more hurt than the time she removed his hand for a picture.