If you've been having contractions and are effaced you could very well be in labor!
ther is no way to know that! My Aunt was 5cm for 3 weeks and 50% effeaced and did not go till almost her due date and my other aunt was nothing and went early and the day she had been checked and the dr said she was no were near going! Labor is differnet with each woman and baby, I say woman themselves know that answer more then anyone else really as they know their body and have instincts.
How big was your first child? I've gone early both of my pregnancies, 38 weeks the first time and then 36 weeks but my kids were normal size and fine. Keep an eye on your contractions, but it could be anytime, you can't really pin-point it. You could go early again, or you could go full term. At this point, I wouldn't do anything to bring on labor though since you are only 34 weeks. You want baby to stay put for as long as possible. Are you dilated at all?