This article on early labour might help HERE.

I had synto with my first and I also had the experience of contractions coming continuously, faster, harder and on top of each other. Below is an extract from our induction article (which you can read here) in relation to effects of artificial oxytocin (labour hormone):

These effects may be partly due to the high blood levels of oxytocin that are reached when a woman labors with Pitocin. Theobald calculated that, at average levels used for induction or augmentation/acceleration, a woman’s oxytocin levels will be 130 to 570 times higher than she would naturally produce in labor. Direct measurements do not concur, but blood oxytocin levels are difficult to measure. Other researchers have suggested that continuous administration of this drug by iv infusion, which is very different to its natural pulsatile release, may also account for some of these problems.