Hi i am 15 days late on my cycle, have high nausea increased cm and headaches but 2 negative hpt. is it possible for me to still be pregnant? confuse

Not likely: If you did the test correctly, at 15 days after a missed period and it was negative, you are not pregnant. You may have hormonal disturbance that is causing these symptoms. Menstrual irregularities are not uncommon and anovulatory cycle is a common cause. If you miss more than two periods it would be time to see your doctor. Consult this site for more information on this topic. http://www.nichd.nih.gov/health/topics/menstruation/conditioninfo/Pages/causes.aspx