Biblically, I think that marriage almost everything was a different thing in those days than it is today

So then we should throw out the entire bible and God's teachings? God didn't tell us "obey my commands but only until 2017, because then things really change and I don't know how to handle that."

It's an extreme example but it's to point out the flaws in this thinking, God knew what He was doing when the bible was being written, and it's not a book that was meant to only be followed for 100 years then we're just screwed after that.

I'm talking about sex in a loving committed relationship.

So marriage, just without doing the actually getting married part?

I have never felt unhappy that my partner wasn't a virgin... I didn't feel emotionally ruined after we broke up.

And why not? If we truly love someone "in a loving committed relationship" should we just give them up like a puppy found on the street when they want to leave?

because we interpret that God tells us so

There is no "interpret", it's VERY clear with no chance of even trying to say it means something else.

1 Corinthians 6:18 Flee from sexual immorality. All other sins a person commits are outside the body, but whoever sins sexually, sins against their own body.

Colossians 3:5 Put to death, therefore, the components of your earthly nature: sexual immorality, impurity, lust, evil desires, and greed, which is idolatry.

1 Thessalonians 4:3 For it is God's will that you should be holy: You must abstain from sexual immorality;

Hebrews 13:4 Marriage should be honored by all and the marriage bed kept undefiled, for God will judge the sexually immoral and adulterers.