Some women do experience flu like symptoms in early labor.
I went in for my weekly OB appt and had absolutely no signs of going into labor....this was on a tuesday. The OB thought I'd go past my delivery date, but I went into labor on that Friday. There's no real way of telling...sometimes you have clear obvious signs and other times your don't. So without a crystal ball, it's hard to tell, babies will come when they're ready. Hang in there. Maybe diarrhea is a sign, but then again you could have eaten something bad. Look for bigger unquestionable signs like contractions that come at regular intervals or your water breaking.