You can loose your mucus plug at anytime. Some people can loose there's and it never effects them or bothers there labor at all.

If you lose your mucus plug a while before labor, as early as you have it will reginerate itself, they shed and reginerate during your whole preg, that is why you have more discharge.

I had passed something that resembled my mucus plug when I was 6 months pregnant too. The doctor told me that it may or may not have been. I didnt pass anything afterwards and I am now 9 months pregnant so I would just mention it to ur doctor that you think it was your plug.