Question about cm

Does anyone know what white with brownish tent mean? Been checking my cm for few weeks and it's been white creamy and then white thick but clumpy idk how explain it. But now it has a brownish tent. Af due 18th. I would say I'm irragular tho. So could it be early sign af or implantation? Sore boobs and mild cramps every so often. Little nauseous every once in a while. Idk any suggestions?