A positive OPK 1 day before period, but BFN pregnancy test.....huh?

Is this even possible? I know I ovulated this month and I have been trying to conceive as well. I am 11dpo today and I have been getting lots of milky white cm (Sorry TMI), and tons of other symptoms that I do not usually get before aunt flow is due, along with one sided cramping that started off on my lower left uterus and radiated all over the rest of my uterus and the cramping has gone from sharp to barely noticeable. I have taken the early pregnancy test and nada! I have been playing around with the OPK and I keep getting a positive result. Has this happened to anyone else? This is driving me nuts! LOL