Brown discharge 10 days before period, for 5 days, very light. (40 day cycle) 3 weeks later no period, neg pregnant test. Could I still be pregnant?

Pregnancy unlikely. Today's home pregnancy tests are very accurate and not affected by foods, herbs, common illnesses, sexually transmitted diseases, vaginal spotting, or medications. A test gives a reliable result 3 weeks after sex (or when conception might have happened) or 1 week after missing a period. If done sooner, a negative result may be due to testing too early, such as less than 2 weeks after conception.