Losing bits of my mucus plug? Brownish discharge?

Just turned 37 weeks today. Went for my weekly check up yesterday and find out I was not dilated yet but my cervix was thinning. Noticed my discharge has been more brownish since yesterday evening. Today, I’ve definitely had more discharge come out and when I went to pee just now, I felt/heard something plop into the toilet so I looked and saw a chunk of brownish discharge. Also, when I wiped, it was definitely mucus-y and little bit of that brown again. Could it be me losing bits of my mucus plus? Or was it just because of my cervical exam yesterday morning?

I’m definitely feeling a lot more crampy and getting backaches lately. Should I wait to call my OB? Any help appreciated!