Boyfriend's parents believe that I hit him. We have been together for three years and have not been separated. What should I do?

This statement itself is nonsense. Now that you know it's superstition, don't take it too seriously. Let's cheat each other. Don't his parents believe this? You can find someone to pretend to be a master, or you can spend money to find a liar who is respected as a master and give him some money to find a way. Master will naturally have a solution, because this is a matter of cheating money. You give him money, his parents will believe it, and the problem will be solved.