Do contractions start out of nowhere?

I need some encouragement. I haven't been emotional my entire pregnancy but I almost cried tonight for the first time. Tomorrow I'll be 2 days overdue, and I know that's normal for FTMs but I am feeling so discouraged. I've had 3 episodes of false labor (at home) and today, I literally didn't even have 1 contraction. Not even BH! I've walked over 6 miles the past 2 days, bounced, tried sex, spicy foods, everything. My sweep last week did nothing. My appt is tomorrow but I know until contractions start or my water breaks, nothing matters. Just looking for some hope that labor could start out of nowhere...?