Confused About a Positive Pregnancy Test and Period - What Does It Mean?

Question
I am 35, with one child (5) and have had one miscarriage (04/04). The start date of my last period was 12/18.  I have been trying to get pregnant again for 1 1/2 years.  I have been using ovulation predictors to assist us.  I started testing for ovulation on day 8 of this past cycle (12/26) because I seem to ovulate all over the place.  It was spiking then.  It continued to spike for next four days.  I was also spotting (brown) On Wednesday (12/29) I had cramps on side and in back and continued spotting. It reminded me of how I felt before my miscarrage (I didn't know I was pregant--miscarried 2 1/2 weeks after a normal period.  Confirmed miscarriage by ob.) I took a pregnancy test to see.. and was positive--showed under an minute.  I have stopped spotting (the next day) and have taking two more tests confirming positives. Date today 1/5/05.  I have appointment with ob next week 1/13. Question--How could I have gotten positive results with no missed period?  Could I be much farther along?  What will confirm how long I've been pregnant?  I appreciate you information very much..It may help arm me with facts or at least questions to resolve with my ob.  thanks for your time.

Answer
Since any pregnancy test will not show a positive result until 10-14 days after conception, and you had a positive pregnancy test on December 29, you must have conceived around December 10 and your last period must have started no later than November 29.  However, you say that your last period started on DEcember 18. The only way to resolve this dilemma is to take a sonogram and see the measurements of the gestational sac. If you really started your period on December 18, and you take a sonogram on January 21, it should show a 6 week sized fetus.  If your period started on November 29, it should show a 7 week 4 day fetus. I would suggest that you do not get a sonogram prior to January 21 because, if it is done too early, you will merely see an empty gestational sac and will not be able to surmise anything. Good Luck.