Well...same thing happened to me with my 3rd baby. I was dilated to about 2-3 cm by 36 wks. I kept having false labor contractions! Then, starting about wk 39, I would have the REAL thing for hours on end. And then they'd just poop out. I finally went into active labor at 41 wks on the nose. Still ended up getting augmented in the hospital, but that was my fault (and the obstetrician, of course), but that's another story.
Here's what I read as I was freaking otu about stalling labors. Sometimes it can happen, because the baby isn't dropping for long enough periods of time. I would suggest walking LONG distances...walk an hour away from home and then walk back once a day.
Another reason is ill-positioning. Sometimes babies are turned sideways (like mine was) or backward or whatever (while still presenting head-down). This can also stall labor a little. Some will recommend that you spend lots of time on your hands and knees rocking. Try to go for 20 minutes at a time, 3-4 times a day. I also read that sometimes taking a hot bath will help relax the pelvic floor muscles a lot. Try laying on your back in the bathtub for about 10 minutes...and then flipping to your stomach for another 10 minutes...can also help to turn the baby.
You might also try stripping the membranes (midwife will do that). The day I went into labor was the morning of my scheduled induction. I had the membranes stripped Monday afternoon...Tuesday afternoon I went for a 2+ hr walk with the kids outside (it was SO cold!!!!)...Tuesday evening, I pumped with the breast pump, one breast at a time for 5 minutes...every 15 minutes or so. I went into labor Tuesday night at about midnight. Was in active labor by 4am with strong contractions. Had to go the hospital, bc I thought my water had broken and got screwed from there. Forced to lay on my back with monitors (for no reason), which stalled my labor a little. The doctor just ordered the pitocin without my consent to start at 8 am as scheduled. He wanted me out by the time he had clinic that day (which was noon). Baby was born at 10:00am.