Am I pregnant? I got spotting only 2 weeks after my period. Never had this before.

I am 39 years old. I have a 5 year old son already. I've had very regular cycles all my life 28 days pretty much on the dot. My first time pregnant, The day my period was due I had spotting that turned to brown spotting and then went away.. I took a pregnancy test and it came up positive.  Now 5 years later.. I've had regular cycles that started the month after giving birth but I am getting older now. I had one missed period...wondering if I was pregnant I went to the doctor to check and he told me I had a cyst.  I had a DNC done the next month  only to be told at the DNC that he doesn't see anything anymore but he will do the DNC anyway to be sure since I already had the shots in the hips.   That 8 months ago in December. Then I was back to a regular 28 day cycle again.

 Last month. I got my period 1 week early which was very odd.  Had sex the day after my period ended so like was cycle day 5.  Exactly 2 weeks after this period started.. I got pink/reddish but heavy spotting that lasted about half a day.. It ended in the same dark brown that I got when I was pregnant with my son. But with my son it was a small drop of brown and nothing more.  I waited 3 days from the day I was spotting and took a pg test and it was negative. I technically should not get my period until 8 more days from now on the 23rd of August, 2012. If I have a 3 week period again. I would expect to have my peirod tommorrow.  I have never had this weird spotting like this but I also had never been 1 week early with the exception of missing the period the one time.

So now I am wondering if it was ovulation bleeding since it was on day 14 or if it is implantation bleeding as it would be 9 days after having unprotected sex. I haven't had any cramping or any other symptons or problems. I'm also wondering if I am going through early menopausal stages since I am 39 now. Anyone have anything similar?