Period due today, but just having a white dishcharge?

Have you had a discharge like this before? Im due to start today, as I am everymonth. We have been trying since Dec of 2011 for our 4th baby! And so far no luck, I am having some mild cramp like pains in very lower abdoment and a snow white discharge. But that's it? Could I be? I tested with a off brand p-test last week and came up Nag Any advice would help!

~Thanks!~