I am 22, on pill and period was due today but now it is one day late. been feeling sick and have brown spotting (preg test negative) pregnancy chance?

Very small chance: Today's home pregnancy tests are very accurate and not affected by foods, herbs, common illnesses, sexually transmitted diseases, or medications. A correctly done urine test will give a reliable result 3 weeks after sex (or when conception might have happened) or 1 week after missing a "period". If done sooner, a positive result is likely real, but a negative result may be due to testing too soon.