Yeah it could be your mucus plus. Nothing to worry about. Just means you are probably starting to dilate. Doesn't necessarily mean that you will go into labor or anything. Some people do some people end up waiting another 2-3 weeks.
It sounds like your mucus plug. How far along are you?
With my first son I had that too and it was my mucus plug that came out
It had brown in it...i got it the next day after they checked my cervix
I had something like that for like 4 days and I told the doc and she said it was probably my mucus plug but if there was no blood or it wasnt bloody looking not to worry