Golf - Why does my ball hook?

Hello, I am a lefty swinger and when I go to the range I can hit the ball 150 - 175 yards, however my ball goes about 100 yards and then slice way left. Of approx. 200 balls I probably only hit one ball straight that had good distance. p.s. I am a baseball player, if that makes a differemce. Anyone please leave me a detailed message to help me correct this problem, Thank You!