I love cheating on my Girlfriend is there something wrong with me?

Ive been with this girl for about 1 year and she is absolutely in love with me, I say all the formalities like I love you but I really am unsure. I have a bad habit of cheating on her because I like the thrill. She has found out about it three times but I was wondering if I should tell her about the other 20 times? I dont really care if it breaks her heart I just dont want her to tell any of my friends. What should I do?