So I've read that some women don't have enough HCG levels before their period to register on a pregnancy test. I already have two children. I didn't test early with them because I never showed any signs before my missed period. So I don't know for sure if I am one of those women whose HCG levels are super low before their missed period. I have taken a few tests 3 & 4 days before my predicted period. They have all been negative. Has anyone ever had this happen?