S.J.
It is possible you were pregnant in October. That happened to me...in June 2007 we were trying to get pregnant and I had my "period" on time July 2, I even took tests during my period (I just knew I was pregnant). I took a test again on July 19 and was pregnant. I actually got pregnant on June 23. After going to the doctor and having a sonogram the doctor told me the "period" I experienced in July was implantation bleeding and the negative tests were a result of low hormone levels at the time of the test (I hadn't been pregnant long enough for the test to detect it).