Well first off, it's not a problem. ;) Some babies, and people, are just bigger than others. The measurements they use are an average so measuring a few weeks smaller or larger is not a big deal. It still falls into the realm of normal. If you were measuring 6 weeks bigger or smaller, now that would be a different story.
My son always measured a few weeks ahead even though we new EXACTLY what day I ovulated, etc. The Drs never worried and, as it turns out, he's just bigger -- 95th percentile -- so it only figures he was large in the womb. I'm fairly tall and my family are all tall. It's genetic. I started to go into pre-labor the day I was induced (38 weeks). He never dropped though and I ended up with a c-s. Frankly, I wouldnt' worry too much if I were you. If you go into labor early, you'll just end up with a c-s earlier. Your Dr willl have a better idea when you get closer. Enjoy the pregnancy while you can. Good luck!