I did something to prove a point and it had a huge impact on my relationship
That sounds a bit shocking, what did you say?
I wanted to prove to my boyfriend that we weren't right for each other and that it was his fault.
Wanting to be right is one thing but what you did was literally sabotaging your relationship and doing that just to win the argument is really toxic. There may have just been something small he could have done that would make you happy or he just needed to hear you say you needed more from him but instead you outright destroyed any chance you two may have had.
It's fine. I don't need him anymore.
Breaking up was probably the best move here. Blaming him as being the only reason is probably not true, have you assessed how you might have done things wrong?