4 tiny dots in underwear??

I have no blood when going to the restroom or wiping with toilet paper, but I woke up with 4 very tiny dots in my underwear. I showered and changed my underwear and after a few hours I had one more little dot, but again, nothing when wiping. I’m 36 weeks pregnant. Any guesses? I read maybe it could be the beginning of the mucous plug coming out? This is my first pregnancy so I do not know what to expect.