PP here...I think the dehydration diagnosis came with 8 weeks to go. I can't remember if the BH started before or after 20 weeks, but I know they came way earlier than in my previous pregnancy. Every time I mentioned it, my OBs said it was normal to have more contractions in subsequent pregnancies b/c the muscles in your uterus had been stretched out, etc. They also told me to eat a banana a day and drink Gatorade, and that I should take it easy, which was difficult with a toddler and a full time job. I didn't go into actual labor until after 40 weeks, and, really the OBs kept telling me not to worry, but it was definitely a stressful time.
If it seems to you like they're getting worse, tell someone! And, be sure to rest and take care of yourself. I had a few NSTs during this time and a BPP near the end that made me feel better. And, the baby was fine. Just my body was worn out.
Hope you feel better!