Losing mucus plug pieces and cramping?

Melena
Probably TMI, but at this point I'm pretty sure not much bothers us, pregnancy can be gross. I've been losing little pieces of sticky mucus for about the last week. I've notice that I'll feel some cramping low in my pelvis, and then when I use the bathroom, there's a small chunk of the mucus. I'm 30 weeks today, and don't have an appointment until next week. Should I be concerned? Or is it fairly common?