I've been on birth control for almost a year now. I Am 4 days late. I took a pregnancy test and I got results within 30-45 seconds. I tested positive. The HCG line was light red. I waited for another minute and the HCG line faded and then it disappeared. Now it appears as a negative test. Is my hcg levels too low to test right now ? Is this really a negative test  ? Has anyone experienced this?