positive OPKs before period? help!

So, I'm suppose to be due in a couple days for my periods. Been having mild cramping & backaches with lots of watery discharge & bloating... I'm on CD27, and last night I took a random opk & it was positive. (Top) this morning around 6:00am, I took another one, (middle), and it wasn't as positive. But just took another around 4:30pm, and it's really positive. What is going on? Is it possible to ovulate this late? What could this be? Helpp