Everyones body is different and there are a lot of factors that play into going into labor, the conditions with each need to be right. Did your doctor happen to mention if your cervix is soft or thin? Have you noticed whether or not the baby has dropped? Try going for walks and or having intercourse...I've heard both can help induce labor if your ready. Be patient and good luck to you!
When my sister had her baby, she was 4-5cm dilated for about 3 weeks before she actually went into labor! So, it can take awhile. I know you're probably very anxious to meet your lo (Lord knows at 38 weeks I was MORE than ready to have my ds out into the world), but seriously try to enjoy the time and sleep as much as possible. Before you know it baby will be here, and you'll be on next to no rest!