I have seen the answers below, regarding Chlamydia and missed periods. I m still not certain they are correct. I have now missed 2 periods, and recently found out, after test results came back, that I indeed have Chlamydia, which I will be treated for in a few days. I am very embarrassed that I even have the STD , as my ex fiance was a lying cheater, and I know he gave it to me. Regardless, I had 2 pregnancy tests , one home and one in a clinic, and they were both negative.. the same clinic that tested me for the STD. I feel like this is a reason for my missed periods, as my tests are coming up negative for pregnancy. Can this at all be possible?