Thanks for the query.
test kits sometimes may not detect early pregnancy and also they can give false positives.
As your blood test
is negative there is less chance for pregnancy.
Your symptoms could be part of premenstrual syndrome
and you may get periods soon.
So wait for one more week and if you do not get periods by that time you consult gynecologist and undergo ultrasound
examination to find out the cause for your delayed periods and symptoms.