When should I really start worrying?

C

So I've been having contractions and getting really uncomfortable for the last hour and a half. I've drank about three big glasses of water and baby has definitely slowed down in his movements. I'm noticing the contractions really only start bad when I'm standing and less when I'm sitting. But I'm 32 weeks and don't want to freak out because this is my second baby and my first I had a ton of false alarms and ended up being induced anyways so I've never been in natural labor. I'm wondering what some signs are that I might be going into early labor so that I can stop worrying about this. I can't call my doctor until morning and there no on call line for after hours. What should I be watching out for and what's a good way to stop the contractions. I'm trying to tell myself if my water doesn't break then I shouldn't freak out. But let's face it. FREAKING OUT A BIT ANYWAYS.