I agree with adgal. Who told you it wasn't amniotic fluid? I would bet it is. Sounds like you lost your mucus plug and have a small leak. I had a somewhat similar situation. I would wake up in the morning with my thighs slightly wet. During the day, I never really noticed anything, so I'm thinking, they say discharge increases, is this that? But I lost my mucus plug on a Thurs and finally went in to the dr the next day (after this happening most of the week). Just seemed like too much moisture. The dr didn't believe me when I told him I thought I was leaking but he did a swab and checked it and sure enough there was amiotic fluid in the discharge. Had to go to the right to the hospital to be induced, and when my son was born he wasn't breathing and turned out to have pneumonia caused by the leak letting in bacteria. Dr said if I would have waited any longer he could have died. He had to stay in the hospital for 10 days, but was fine after that. Don't want to scare you too much but I think you really should get it checked. If it isn't, well, then no harm done. Better safe than sorry. Good luck! (I was 37 weeks also)
I'm sorry I can't be much help here, but if you suspect you might be leaking amniotic fluid, I would suggest you see your Dr. I think that is an important thing to mention him/her about. Good luck to you.