Do you think that morality has a divine origin or that it has a human origin (whether sown into the fabric of humanity/nature or a human construct)?
If you believe that our values and morals have their genesis on the plane of the anthropological, then why ask the question you have asked? Simply choose what you want to do (i.e., what you want to be the right thing) and to hell with the opinion’s of others. If you feel it is right, then, in the words of Captain Picard, “make it so.” After all, if we construct our own morality, then why not be an individual and create your own. Why follow all the sheep and ask “what ought I to do?”—none of the sheep possess any moral authority that is more authoritative than your own; you alone are in the primary position to govern your own thoughts/actions. In fact, if you inquire of the herd, they will only give you their own brand of morality that typically favors them (assuages their fears, looks after their interest, strokes their vanities, and is designed to keep you at their level). And, you will have as many opinions as you have sheep (although some agreement between them will obtain).
If you believe that right and wrong descend from above, then I would suggest you begin a spiritual quest to engage the moral code of one of the world’s great religions and incorporate it into your life. Most of these will probably forbid sex before marriage at all—so your original question has a moral question mark put against it at the outset. You will become very unpopular if you do this. Why? Because you will actually believe in something to your core and will follow this despite what others think or say. Others will find this unbearable for various reasons (pride, jealousy, fear being just a few). The moral doctrines of most of the great world religions don’t coincide well with contemporary Western society. If you have integrity and really practice what your religion teaches, you may find yourself being marginalized; many can’t bear this so they compromise and, in the end, think their religion morally bankrupt and not themselves.
Or, there is the third “slacker” option—which is what most do. This is the “follow the herd” option. Don’t allow yourself to be bothered by all this sort of thing I’m talking of. Just lazily consort with the opinions of others, after you ask a handful, you will always find those who will basically agree with you and then you can justify anything you want and all the while hid from yourself the fact that you are doing this; this way you never have to take responsibility. Console yourself with the fiction that since others say this is the right or proper thing to do then it must be the case. From time to time you will find more that disagree with you than agree with you, at these times you may have to desist from some action but then you can always use this as proof that you are enlightened and a moral person.
Some may tell you that the option of spirituality/religion is nothing other than the first option outline above (constructing values/morality for yourself) dressed up in grand clothing and ensconced in time honored teachings. They will argue that religion is just a mask; a mask that hides the fact that right and wrong are really arbitrary and truly are simply relative (just like they are in the “constructed” model). But most are not really in a position to say this. They are not privy to the experience of the power of such a religion. That is, those who truly believe in their religions enter into a domain of experience that puts them in a whole different class altogether. They truly believe that what they are doing is right and this brings a whole dimension of certitude and singleness of purpose that escapes the “constructionist” types. What I am saying is that when you look at it from the outside, the truly spiritual person, seems rather na?ve and misguided. Somewhat to be pitied for they enter into an allegiance with seemingly silly and outdated notions. But from the inside, the spiritual enter a whole new world that operates on an entirely different set of rules, within a fundamentally different framework, a world that certifies itself on its own terms. Thus, those on the outside are, in one sense, are in no position to judge those within this new world and framework since they know not of what they speak and judge.
Lastly, others will eschew the term religion and quest for some sort of spirituality of their own making. This is probably the worst form of “constructionism” out there. Because now you have those who invent their own morality but have coupled it with a quasi-religious fervor! They bind themselves to nothing but aspire to be “spiritual.” Beware these types.