Actually, Tikeyas Mom, I meant to reply to your thread earlier about your mom.

I was going to suggest what's called a "chemical pregnancy".
It was suggested to my cousin recently that she was having that. Your body thinks you are pregnant, you have pregnancy symptoms, and if you take a urine pregnancy test, it will come up positive. However, a blood pregnancy test will show up negative.
Also, I don't know how young or old a woman can be in the case of a chemical pregnancy, but my cousin is only 34.

Sounds like that is what happened in your mom's case...but in my cousin's case, she had her tubes tied a year and a half ago and now she's really pregnant again!