You should always be honest about your feelings in a relationship regardless of what else is going on. If you aren't then you can't be upset when it goes wrong. He took you up on the idea that you two had a physical relationship and then he met someone who wanted more than a physical relationship. By not disclosing he saw more potential in the other relationship or he just used you for sex. Either way he didn't have all the information. It could be that he played games and you should be glad it's over. I would tell you to move on at this point.
Try to find another way to relate to men. You probably reacted to the uncertainty he was creating but for the future dont allow a guy to take you away from being an honest up front person. He could just be a jerk and you are benefitting in the end. A guy doesn't meet one women for sex and another brand new woman the next day and commit to her. That leads me to believe that he was doing this already. Let this go. You aren't in love yet
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