Someone help?!

Okay so I'm expecting my period next Sunday. Today I went to the loo and noticed some discharge... I also had some very light brown/pink colour discharge, I have been gettin stomach cramps like mild pmt pains the last few days and I had been very light headed. Another thing which never happens is that the past 2 days I've been waking up bursting to go to the toilet for wee and really thirsty and going really hot and headaches...