How can I tell if I might possibly go into an early labor?

I'm 31 weeks pregnant, and lately I've been experiencing certain things which are making me a bit nervous that I may be popping sooner than later. I can definitely feel that my baby has dropped. And for the past couple weeks, I've been having diarrhea, random bursts of energy, leg and back pain, and a huge increase in my braxton hick contractions. Also, just this past week I've lost 5 pounds. Should this be of any concern? Does it sound as if labor is approaching quickly? I just want to be prepared!