Your vaginal discharge will get thicker and heavier late in pregnancy. This is more than likely not your mucus plug. If you start having bloody discharge or an odor, or thin watery discharge, go to the hospital immediately.
This started happening to me at about 35 weeks exactly what you are describing. The day before my water broke at 38 weeks I had the bloody show. I hear that it can regenerate itself if you do not go into labor also, which is why it can happen for a while.
Definitely could be your mucus plug! It is thick like snot and looks a lot like it! I've had 3 little ones and man it can either come out slowly or all at once in a big nasty bloody mess! So if you have a bloody mess in the toilet don't freak out! I did when I had my first, thank God I was in L&D to be monitored when it happened the nurse reassured me everything was okay. Good luck! But if you see that be sure to call your doctor!