Is becoming fixated on people a sign of low self-esteem?

I have always had a tendency to really become fixated on a guy if he even shows a little interest in me. Maybe I want to have a relationship so much I feel I'm willing to work hard at it. I just wondered if this is a sign that I don't value myself. Most of the time, the guy turns out to be a player, my feelings get hurt, and my heart is broken. Not sure how to get past this fixation tendency. Any thoughts?