Why do guys who are taken hit on me?

What is it that i put out there? That makes guys with girl friends think its ok to try and kiss me or profess their "love" for me? I do not flirt. I am a playful girl, i dress modestly, i just am very easy going and act like myself. I have had 6 taken guys try and pull something on me in the past 4 months. I don't understand. Do they see me as just a girl to fool around with? I feel like I only attract guys who are in serious relationships. Why can't single guys like me as much?