Belly foot is swollen, my period ...

The foot of my belly is swollen my menstruation was to have come on 08/19 but a brown discharge came 4 days before it stopped on the day it was to have gone down, only it came very thin and on the third day did not descend anything. Just as the discharge came down I felt a little pain. And my belly is growing gradually and I feel nausea dizziness too much sleep, tiredness 10 days after the 19/08 I did the blood test and gave negative.You have any idea what it may be? Ahh and I do not take the pill. I await your reply.