It sounds like you're experiencing a lot of stress and anxiety about your current situation. The dark brown or black blood you're seeing is likely just older blood being shed, which can happen during a period and is usually nothing to worry about. Regarding the pregnancy test you took two weeks after your period, it's generally accurate at that time, but it's understandable to have doubts. Stress can sometimes interfere with our bodies and minds, so it's important not to let it take over. However, if you're still feeling uncertain or worried, it might be helpful to schedule an appointment with a gynecologist. They can provide you with more information and help address any concerns you may have.