Hello,
I'm going to chime in there and say that I am now 6 months pregnant and that's exactly what happened to me - but back in June :) I had a normal period in May, a day of spotting in June, and now I'm 6 months along. BUT, if you've had 2 negative tests, you may not be pregnant. Have you been under any stress, added any new meds, changed your diet, went up and down in weight at all? Are you using first morning urine when testing?