It's NEVER a good idea to sleep with someone just so you don't lose them. It doesn't work also because if the person is nice& cares about you- they'll understand yr not ready for sex& they won't push it.

If the person's only in it for the sex, of course, they will leave you. But the irony is that they would leave anyway once they've had the sex - or a new conquest comes along because they don't really care about you. And you'd feel ten times worse because you gave up yr values for someone who took yr virginity and then treated you badly and left you anyway.

If this boy is as nice as you say, just tell him you like him but are NOT ready for sex and don't want to be pressured. If he really cares for you, he will understand. If he doesn't, then he' not worth it. And better he leaves before sex than after sex. You'd feel so much worse if he sleeps with you then leaves. Never give up yr values or do something yr not ready for to please another. There will be many men willing to date you without forcing sex on you till yr ready. Be honest and don't do something you'll only regret later. good luck.