I wake up with that too most days, just a mild kind of sensation. I thought it was an infection as well but my surgeon assured me it wasn't. Having the lube remain clear after dilation, no fever, and no terrible odors seem to indicate there isn't anything wrong. However, I'm on my second course of antibiotics from my primary doctor, who'd rather be safe than sorry, especially since I have a little spot of granulation tissue/tearing that was oozing a bit. I'm 8 weeks out and this has been going on about 3 weeks, and seems to be getting better.
I was told that the sensation can be from nerves reconnecting. Moving up to a bigger dilator seemed to help. A friend said that it may be because the tissues are getting compressed which helps settle things down instead of everything just kinda hanging out and getting overstimulated.