So discouraged

So my period is due on Sunday. The past couple of days I have felt like I am in a fog and my boobs have been a little sore to the touch. I have also felt a little nauseous after eating some foods and omg I have felt so exhausted and tired when I get home from work. Took a test this morning it was a Walgreens test and it was negative. Anybody have problems with those giving false negatives. I haven't used that brand before or do you think I just tested too early