Labor signs

So I'm 31 weeks and 3 days pregnant today, and last night I couldn't sleep because of an ache in my back and a pain in my pelvis. I'm not sure what it was, my baby has been moving throughout the pains, but I feel like it might have been contractions. I'm scared that it's going to break my water, or something dangerous might happen. I'd like to keep my baby in until at least 34 weeks. Maybe someone could explain how contractions feel, I and how to know if your water breaks? I know it's different for everyone and it's not like the movies. Please help a girl out.