Fetal Fibronectin Test- Please help!!

Miranda
I received a call back from my OB after calling the office due to feeling like my pelvis is broken.  I have felt this way for about 12 weeks but it has steadily gotten much worse.  I have googled and tried numerous remedies to try and relieve the pain all to no avail.  My OB recently told me that my cervix has shortened a bit and that he would continue to monitor it.  As of last ultrasound it had shortened even more and he will continue to monitor it over the next few weeks.  I received a call back from his office today scheduling me for an appointment tomorrow morning for a Fetal Fibronectin Test.  The nurse briefly explained it and afterwards I googled it to gather more info.  I'm just curious if any momma's have had this done and if so was it accurate at determining preterm labor?  I'm a bit scared because with my first pregnancy 16 years ago I had preterm labor but luckily the were able to stop it before it progressed too far.  Please help!!