Ladies

Is there any other things that could cause a missed period? I don't have insurance yet, I'm in the process of getting it, I am 4 days late and the test I took this morning was negative, along with all other tests after that.. my only symptom is nausea and tiredness.. right now I have a really bad chest cold along with a sinus infection, I'm losing hope because I should at least have a faint line by now!