Late period, pregnant ?

I have been off birth control for 3 months now. I finally think it's out of my system because I am starting to break out again. I am about four days late and I am having cramping but no period. At times I wake up and feel a little nauseous but not sure if that's from eating late at night. I took a test and it was negative though. Was hoping that this was my month to get pregnant with our first child. I have been very depressed lately because I want a child so bad. I don't have any other symptoms besides being tired alot, but I work and have school.