Alarmed!

Over the past few days I have been loosing my mucus plug in chunks. I have spent 2 afternoons in L&D; being checked out and numerous tests run. I am not dilated but my cervix is thinning. Dr ran a test that is a good prediction of going into labor within the next 2 weeks, but it came back negative. Again, I am continuing to lose pieces of my mucus plug, little man's head is SUPER low, and I can feel my vagina pulsating. I am concerned that I'm going to go into labor any day now. I am currently 34 weeks and this is my second baby. Anyone have advice or been through a similar situation before?! Thank you for your comments!