I absolutely agree with you. You are not old fashioned, prude, naive, stupid or watsoever today's world will call. Your convictions are worth it.So stick to them and don't care for people saying anything, afterall its your life and you will have to pay the price of your doings.
These realtionships won't get you anything except for depression, feel of being used once someone dumps you because there's always chances of nyone falling for you seriously and if one of them is not interested then it will definetly gonna land you in hell.
So for me its a complete NO! NO! and it looks good only in confines of marraige.