Start messing witch chicks that have something to lose.
Knowledge is the best contraceptive. I had the same thing happen to me when I was 20 with this girl I dated for like 3 months. Broke up with the bitch and a week later she calls me and says "I'm pregnant". Fast forward 9 months the baby is black and your boy is off the hook. I straight went on a 3 month bender it was like the best moment of my life.