Joey, The pain your probably experiencing is the baby pushing on your cervix. At this late stage when the head drops into the pelvis ,the babys head movements can irritate your cervix causing these sharp short pains. This is all normal and a good sign that your bub is where he/she should be.Contractions dont start that painful its more a gradual build up ,and for me a LOT of pressure.They will also leave you breathless and unable to walk.
Braxton hicks are like the same feelings when the baby pushes hard from within, but the baby isnt causing the hardness by pushing . God , did that just make any sense. This is how it is for me anyway. others may have different experiences.
Hope I was of some help and didnt confuse you too much.