I am thinking about my ex girlfriend for a long period of time, she was my first love, I have relationships with other girls, sex etc, but everytime my mind goes back to that girl. We didn't contact since we broke up. I saw her maybe 2 or 3 times in past decade and everytime I saw her I felt like I am gonna collapse. I dont have desire to call her or see her but somehow she is still in my head. Is that normal?