The start to REAL labor?

Kelly • Wife to Steven ❤️ • Mommy to Steven Micheal & Avery Grace 💛 • Jeremiah 29:11
OKAY ladies. I just want your thoughts. I am currently 40 weeks and 4 days pregnant and today around 12pm I had mucus plug come out tinged with blood. Since then, I have been getting inconsistent contractions here and there. 
Nothing too out of the ordinary though because this is my second pregnancy and have had these contractions for a little while now. 
BUT - for the last few hours my lower back has been HURTING so bad - and I am still having irregular contractions, and they seem to come more when I move around...
and when they come, my back hurts worse. 
Do you think I could be in actual labor? My instincts say yes, especially since I've done this before, but I do NOT want to wait to call the doctor, but at the same time I don't want to go into the hospital only to be sent home. So annoying!!!  
Update: Also having diarrhea.
Another update: contractions are coming every 10 minutes now.
Update! IT WAS LABOR! She came the night I made this post.