Most girls that have their first consensual sex go into the bedrooms thinking the same exact question you're asking. If you TRULY don't want to have sex, I advise you to just not spend a night together. I'm not saying he'd rape you or anything... But the situation, being in bed, the intense feelings, and the physical contact will make you want more... Now because you want to feel each other more, you start taking taking clothes off. Next thing you know you've used the backup condoms he had brought. Sexual desires aren't easy to hold back... Especially in perfect conditions like this.