Getting Nervous

We had a check up with the midwives today. 24 weeks 5 days due November 24. So far the baby seems to be doing well but I was told today that we are measuring 4 weeks ahead. I have been active and only going 1 lb since me last visit about 5 weeks ago. I'm not a stickler for birth plans but I have two other kids to plan care for when Marjorie decides to come. Is she going to be early? Was she just stretching when I was measured? Should I plan on delivering a toddler in November? I truly feel huge and like I've been pregnant forever. The arthritis in my back and hips is not helping any either!