Cindywon - I can't tell without looking at you, but I'm guessing you are losing your neutral pelvis position when you go into the drops. (if it only hurts in the drops). This could be just a posture habit, or it could be core that needs more strengthening, or it could be bars that are just too low for your body mechanics (making you get lower than your body can do functionally).
The easiest thing to try is to hold in your lower abs (like when you cough or laugh) and go into the drops. Do you still land on the hurting part? (if "no", then you just have a habit or core strength to work on) If the only way you can stay off the painful part is to curve your back, or if you just can't stay off the painful part at all, then the next idea to try is raising your bars.
Saddle postion comes into play here, too. (like you may be sitting on the nose part a little more if your reach is too far, etc.) I'm assuming your saddle is in a good position for you. But if you can, get someone to observe you on the bike.
I'm sure you've seen this book recommended a gazillion times, but I'll wave it around again just because it's such a good book: Andy Pruitt's Complete Medical Guide for Cyclists.
"If Americans want to live the American Dream, they should go to Denmark." - Richard Wilkinson