Delayed Period & Negative Pregnancy Test: Possible Causes & What To Do

Question
Hi,
I'm 33, have one child age 12, and last period 1/15/06, very regular 21 day cycle. Just started trying to conceive first of Jan. Periods very regular, started 15th ended 21st, ovulated I think around 27th (light brown spotting x 2 days). Period due Feb.4. No period, but had all symptoms, never, ever, late! Blood test negative hcg, last night Feb.8, clear, eggwhite stringy cm. Today some extremely light spotting. What is going on? I just knew I was pg. Is this my period just late? Usually heavy flow and 21 days to the day.
Thank you

Any response greatly appreciated.

Answer
If you have a 21 day cycle (from the first day of your period until the first day of your next period) ovulation occurs on cycle day #7. (Ovulation always occurs fourteen days prior to your period). If your last period started on January 15, then you were due for your next period on February 4. The best time to do a pregnancy test is seven days after missing your period. Therefore, any time after February 11 is a good time to take a pregnancy test if you do not get your period by then.