Finally felt the baby move?

I'm a FTM and as of today am 18+1 weeks. Everyone keeps asking me if I've felt the baby move yet, and I was getting nervous that I kept having to answer "no". (My first pregnancy ended in a missed miscarriage, so I've been nervous a lot this time around.) Anyway, I think I finally felt baby move this weekend! I can't describe the feeling, but it happened twice. Both were at night, laying in bed amd almost asleep. I'd feel something that shot me right awake. It didn't feel like the butterflies women at work described, but I don't know how to describe it. What did your baby movements feel like? How did you know it was baby? Thanks!