What is up with my uterus?

So, my guy was visiting from out of town at the end of January, he was here for 5 days.  I am not on bc pills, but during that time we used condoms, pull out, and the sponge.  The day he left, I also took plan b. 
My February period came early, but with all the normal pms symptoms.  However it was very light, and only lasted about 3 days.   I took a hpt (2 actually) and both were negative.   I took one a little later and it was also negative. 
The problem is that according to Glow, my period was supposed to have arrived on the 12th, and while I've had a little cramping and tender breasts, my dear Aunt Flo has yet to arrive. 
Any thoughts?