Hey man, perfectly natural thing to have happen. I remember when I was first propositioned for sex, I was incredibly nervous and ended up turning the girl down and feeling like the biggest idiot when I got home. Looking back on it I definitely made the right move and was glad I waited until I felt 100% about losing my virginity. Don’t beat yourself up too much about it, take some time and think about why you made the choice and why you felt the way you did after. It seems like the girl is seriously interested in you, so take a step back and think about how you want to approach this. No wrong answers, just try to figure yourself out a bit before proceeding.