Hello, You have missed your periods, you always have unprotected sex with your partner. Your pregnancy tests show negative report. Your blood test for pregnancy shows low chance of being pregnant. You smoke marijuana daily. Cannabis is likely not to affect the outcome of a home pregnancy test. However, the chemicals in cannabis (THC) can harm a fetus. Get clinically examined by a gynecologist, get per vaginal check up done to detect the size of the uterus. Get a USG(uterus and fallopian tube ) done to confirm pregnancy, ectopic pregnancy or any other pathology that is causing you symptoms. If pregnancy is confirmed. Work on quitting Marijuana smoking with the help of a detox center. Marijuana smoking during pregnancy has the probability of affecting the baby s development. It poses the risk of complications during pregnancy like low weight at birth, premature birth, still birth, or a small head circumference, which are a few. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician