Its selfish because it is going against what God wants you to do. Therefore you are saying you dont care what God has said about sex, you push his view away and think of yourself...you think it is your way....and thats that.....but God will set it straight on judgement day.
The Bible does have a lot to say about sex. Oh yes indeed!
According to Deut. 21, if a man sees an unmarried woman that he desires (after he's done sacking the city she lives in), he can simply take her to his home, let her mourn her parents for a month, and then
by the act of having sex with her, she becomes his wife. The man didn't take the woman somewhere and get married first, no no...
According to Leviticus 18, it is against God's will for even a married man to have sex with his wife during her period. I wonder how that's going to read out on judgment day.
Also by Deut (this time chapter 22), it isn't necessary at all to go through the hassle of getting married before having sex with an unbetrothed virgin. If you rape her, all you have to do is pay her dad some silver and
then marry her. Then everything is a-okay.
Deut. 25 commands men to have sex with their brother's wives. Yes indeed. Under certain circumstances this is God's command. If the woman's husband dies without having had a child, the man's brother is
required to have sex with her.
It's also quite clear from the Bible that God condones and allows men to have multiple wives. There are laws for how to treat a second wife (Exodus 21:10, Deut. 21:15). As well, all the laws concerning marrying a woman that a man rapes make no mention of what happens if the man is already married. Clearly that didn't matter... she just became yet another wife.
Now, is that
really the kind of stuff you believe God wants us to do, concerning sex and marriage? It's right there in the Bible, after all.
(And wouldn't you know it, I can't find anything anywhere that says sex before marriage is prohibited.)