30 weeks belly dropped?

I've been having pretty bad diarrhea the last day or so, intense pressure way down low, and slight cramping. Typically when I'm getting ready to go into labor this happens first, my belly drops, and then water breaks :( do you agree that my belly has dropped! I want to stop anything from happening before it can actually start.. All of my kids have been preemies, and I'm trying so hard this time to catch it (it being going into labor) as early as possible.