lost mucus plug

Kelly
I'm pretty sure (95%) that I just lost my mucus plug.. I'm 29 weeks today and have a history of preterm labor and births with my two other babies, but not this early. Could this mean anything? I know that typically it can mean labor is near. I haven't had contractions but I have had strong back pain on the left side of my tailbone since last night. I assumed it was round ligament or something. Thanks ladies