It does matter.
And it is ‘our business’ as human beings. As human beings we are concerned not only with the state of our soul, but with the state of our ‘neighbor’s soul.’ Not in a punitive, aggressive, “you sinner!” way, but in a loving, helpful, “my brother/my sister, you’re in danger; if you don’t want my help I won’t force you, but I also won’t let you go into danger blindly” way.
This country has seen now a few decades of living ‘the way I like, because it’s nobody’s business’ and it has led to countless thousands of impressionable young people --from infancy onward–being exposed to vice and sin. . .and that vice and sin not presented as abnormal and wrong, but as so ‘normal’ that people shouldn’t even pay ‘attention’ because, “It’s nobody’s business what my boyfriend and I do!”
If you’re living with your boyfriend without being married. . .and yes, even if you’re living ‘chastely’. . .what message do you think that sends to the little children, the teens and other young adults that you don’t even know but who ‘know’ you from seeing you as neighbors?
You don’t live solely ‘for yourself’ or ‘for yourself and your boyfriend.’ You live in a society, and your actions leave an impression on society. Good actions leave good impressions. Bad actions leave bad impressions. The more ‘good’ actions, the better society will usually come to be. The more ‘bad’ actions, the worse society will usually come to be.
The more we live selfishly (and this is really a self-centered attitude as the people involved really don’t seem to either know or care if others are negatively affected, as they think it is** only their business)**–the more selfish we grow and the more selfish others grow as well.
You could, indeed, be living ‘pure as the driven snow’. Why people must needs ‘live together’ instead of apart until the marriage is most probably economic --the idea of maintaining ‘two’ separate places probably seems ridiculous when people could ‘save’ by having just ‘one’ place. . .but money and economics aren’t everything (and believe me, I am dirt poor myself so I’m not speaking from the ivory tower standpoint of somebody who’s never had to scrimp, save and even go hungry and cold on a regular basis).
Living together without being married is dangerous. One falls into ‘occasions of sin’ and while one might be able to fight them off, there is always the chance of losing a battle. . .and the more battles there are, the greater the chance of eventual loss.
Sin is usually presented as ‘glamorous’ and quite often as ‘innocent’ in nature. . .it’s the ‘dirty-minded’ we seek to ‘blame’ for the situation, not the person’s own choice in choosing to live with a boyfriend/girlfriend. IOW, it seems that they want to have the moral comfort and superiority of ‘doing the right thing’ even though it LOOKS ‘scandalous’ and turning the ones scandalized not into their victims but into the sinners themselves. I don’t think that is right, nor is it charitable, to blame others for making the reasonable supposition that two people, male and female, calling themselves boyfriend and girlfriend, and living in the same place, are possibly (though not certainly) living in sin. . .because the appearance of the sin is there. Remember, observation is not necessarily 'judgment. This is why I’m pointing out to you that there is a danger. It is a danger not only to those who in all reason and fairness are REASONABLE in assuming that you COULD be living in sin because the majority of men and women in that situation are indeed living in sin, even if you personally were not. It is a danger in that you are ignoring their being scandalized and indeed turning them into the ‘villians’ of the piece for ‘not minding their own business.’
A woman should not be living with a boyfriend (or a man with a girlfriend) outside of marriage. I’m sure people think they have excellent reasons for doing this, particularly if they are not ‘intimate’. . .but all those aside, you know it has the appearance of scandal, and you know that in the last 40 years or so it has been the incredible explosion of people who DO live outside of marriage in sin which has been a cause of many dreadful breakdowns in society, and further led to more people committing this same sin because it was become so ‘commonplace’. And many Christians have fought against this ‘societal assumption’ that this situation is ‘fine’ or 'nobody’s business but the couple’s. And that fight is made harder every time another couple does this, even if it is only in ‘appearance’.
So. . . it matters. You may not be guilty of personal sexual sin, but the scandal remains. . .and the danger for you remains. . .and may God protect you and guide you to doing the right thing.