Feeling movement 16 weeks.

So, for the last few nights I've felt like I can feel baby moving. I didn't know if it was gas or what but tonight I was laying in bed and I felt a pop right below my belly button that was unmistakable. It couldn't have been anything else I've never felt it before. But I also notice that I have more cramping at night too. If she is moving could that be a reason for the cramping. I feel like she just might be super active at night and that's why I can feel things and have more pain. I'm so unsure, haha. Any ideas?