I had the same thing with my second pregnancy (soaking thru a couple thin pads a day). I swore to the doctor that my water was leaking and even ended up in the L&D unit at the hospital to have it checked a couple times. They can do a really simple and non-invasive swab test to find out if you did indead break your water. It's kind of like a long Q-tip that they have you cough and swab your vagina (the coughing part supposedly makes the water flow if you did indeed leak). It has a reactive chemical that changes color in the presence of amniotic fluid.
Turns out, I never was leaking. Must have just been thin watery discharge or urine. I know as gross as it sounds and as much as you swear you are not peeing yourself, it happens...especially this late in the pregnancy. Baby is pushing on your bladder and your muscles are getting weak from being stretched out and not used as much...and it just kinda dribbles out.
Have no fear. You are not alone...not the first, and certainly not the last. If you are really concerned, call the doc. They are there to help you, so don't feel as tho you are abusing the system.
Good luck and congrats!!!