I had GBS with #2 also and felt the exact same way as you. I took the caster oil and it have me INTENSE contractions for about 3 hours and then stopped. I say don't take it.
There aren't really any studies that show castor oil really works. I have always heard its an old wives tale. And be careful what you take because lots of things can interfere with the effectiveness of antibiotics...
I dont' agree with castor oil either. At this point it really isn't adviseable to be trying so hard to get your baby to come out. Typically speaking, when a babys lungs are mature the baby releases a hormone that triggers your body to begin the process of labor. Occasionally this doesn't happen which is why some people end up with inductions etc. Baby needs all the "baking" time s/he can get in order to ensure the lungs and other various functions are fully mature. As for the GBS, your doctor should administer IV antibiotics while you are in labor to help reduce the risk of baby getting it. The risk of baby developing any long term affects is minimal. (98-99% of all babies born to infected mothers will not become infected, if treated. Of those who become infected few will have any problems with the treatment for the infection)
I would never recommend taking castor oil since that can cause horrible problems to the baby. Babies are recommended to stay in there the full 40 weeks since they are still developing. Even though its considered "safe" to give birth at 36 + weeks its not recommended since sometimes even at 40 weeks baby isnt fully developed. As for GBS, I had it with my last pregnancy. My water broke at 38 weeks and I wasn't experiancing any contractions or anything. I went to the hospital and they hooked me up to the IV with the medication and induced me. It doesn't matter if your water breaks or you go into labor on your own just that you get the medication into your system before the baby is born.
be careful with castor oil..some people believe it can cause the baby to pass meconium (baby's first stool) which is supposed to be passed once the baby is born. if its passed while in utero the baby can inhale it and suffer infection/respiratory problems, etc...
all castor oil is is a laxative. because of the bowel stimulation it CAN cause contractions...but that probably won't do anything if your body isn't ready. plus you are already experiencing contractions (same as me). those can help to dilate and thin your cervix.
the best thing you & i can do at this point is to try to help our cervix dilate. walking, sex, etc...i am 1 cm also and i know how frustrating it is. 1 cm for 37 weeks is actually pretty good.