It's possible, but as long as you like someone else, you can tell your girlfriend frankly and break up with her. Don't be a fish in a pond. Don't say that falling in love means that your heart may change after marriage. Fun is instinct, loyalty is choice. A good man doesn't necessarily have a temporary crush on other opposite sex, but chooses to be loyal to his marriage. Understand the fickleness of human nature, so that you won't be hurt.