Hi, I think I'm pregnant but i've had negative pregnancy tests within the course of 2 weeks. I had sex from Sept 9-12 and on the 13th I missed my birth control pill and on that Monday Sept. 14-16 I had light spotting that had a pinkish red/brown color. My last period that I'm sure about was 08/20/2015. Ever since the spotting occurred I've had consistent headaches, nausea here and there, lower back pain that just recently stopped, bloating, fatigue, gas, and constipation. I'm not sure what to do or what it is please help!