Ay, 28 weeks pa lang kaya unlikely na mucus plug na yan, mama! The mucus plug usually comes out closer to labor (usually around 36-40 weeks), so what you're seeing is probably just normal pregnancy discharge which can get thicker and heavier as you progress, a few of us went through that phase din and nag-panic kami haha. That said, if you're worried or if may strange color, smell, or it's accompanied by cramping or bleeding, it's best to check with your OB na lang para peace of mind, especially with the other changes happening in your body!