Ryan -
Immorality is defined differently by different people.  It's not about shifting moral values.  You have no more or less authority on immorality than the rest of us.  We all form our ideas of right and wrong based on the evidence that we see.  Yours has been different from ours and you've concluded that premarital sex is, without question, immoral and wrong.  Others have made different interpretations of similar and dissimilar experiences, and have determined that is isn't always immoral and/or wrong.  

My evidence is my own experience and the reality around me.  Studies show that almost all people engage in premarital sex.  Scientists have studies the effects of it on the success of marriage, and while there is a small correlation, they suspect that part of the reason they see it is because of people, possibly similar to you, that are determined to be (or act) happy because they are <i>supposed</i> to be to fit into a label that they cling to.  I think honesty and living a loving, compassionate life is more important than worrying about premarital sex.