different resaults

hi, I had my first pap in march 2003 and it was abnormal. I kinda forgot about it and didn't go to the doctor again.
my second pap was in may 2007, it was abnormal again, so I got a biopsy done and the biopsy resaults were normal.

so now I had my third pap in february 2008 and it was abnormal, so I got a coloscopy done and through the coloscopy the doctor found hpv.

I am married and I haven't cheated on my husband, neither has he. but we had partners before our relationship.
I know that hpv can be shown after many years after the infection, but how come they found hpv throught the colocscopy, but not through the biopsy last year!

is it possible that I had the virus in me, but you couldn't tell with the biopsy?