anyone know what it is?

Im 39 weeks and ive been spotting bright red blood. Its not a lot or any thing and im not super concerned. My baby still moves and kicks a lot I was just wondering if anyone has gone through this and knows what it is. I called and the medical assistant says its part of my mucus plug coming out, but its not mucus coming with the blood (like its just blood and discharge sorry for the tmi) so if anyone knows what it is please let me know