There is a difference between a sex urge and sexual activity. Men think about sex quite often. According to some of the better research the greater frequency may be nearly three dozen times a day on average. So the urge and the thought may not be as abnormal as you might think.
However, the experience of constantly falling in love and getting hurt is a different matter. It sounds like you may be falling for the wrong people. Perhaps the most direct way for coping with this is to find a group therapy practitioner who works with men and women in the same group. This can help sort through your reactions and allow you to learn more about finding people who will reciprocate your feelings.