Feeling sickly right before labor?

Momma of 4
I've heard of having a sudden burst of energy right before birth, but what about feeling sick? I have this "I'm coming down with something" yucky feeling but no real illness symptoms (no sore throat, fever, diarrhea etc), just feeling quite unwell in general. I'm 39 weeks have had prelabor symptoms off and on for about 2 weeks.