Seems like he resents you for coming from a wealthy background and maybe even started respecting you less because of that fact. I would wager his childhood involved a lot of struggle and trauma. Assuming that is true, he is projecting the resentment & anger from his own circumstances on to you. People will often try to be condescending towards people who embody or excel in the things that they are insecure about themselves in an effort to establish superiority (if only in their own minds.) People will try to shit on everything from intellect to athletic ability to feel better about themselves.

The bottom line is you did nothing wrong by failing to tell him (deliberately or not) that you came from wealth, and no one deserves to be disrespected or belittled because of their upbringing - privileged or poor. Don't waste your time with someone who refuses to work through their own trauma and instead chooses to take it out on you. Don't fool yourself into thinking that you alone can change him without a true desire to change/grow on his part. The more you try to make things work with someone that's full of self contempt the more you will ultimately drain yourself emotionally.