Self-inflicted bruises

I really enjoy bruising myself. I tend to repeatedly hit my thigh with the base of my hand (think the bottom of your palm, close to the wrist) until it becomes red and swollen. Usually it turns into a minor bruise by morning if done at night. I don't know why I enjoy it, but the pain does not bother me and I like the aesthetics of it. I am no more depressed than everyone else (that is to say, not clinically). I have never hurt myself on purpose in any other way (cutting, etc) Just wondering if it was normal.