Have you ever done anything to spite your partner, even if he or she will never find out?

I have started doing little things that I normally would never do, and I think it is because I know my boyfriend would disapprove and even be angry over them. I guess I've started to feel really resentful towards him because of some injustices that he has put on me. Whenever I try to bring it up so we can talk it out and I can tell him how I feel, he makes himself into the victim. Even though he will never find out these little things I have done to get back at him, and even though they are not harmful to anyone involved, I know it's not a healthy way of dealing with things. Aside from this, we have a really wonderful relationship. Have any of you ever found yourself doing something like this? And if so, under what cirstances, and how was it resolved?