Same thing happend to me, my biopsy (through colposcopy) came back neg too. I was worried about it the whole time, but since then i have heard more stories from friends about the same thing, that most women at some point have an abnormal pap, but often the follow-up is neg. Some cell changes in the cervix resolve themselves on their own within six months. I know it's impossible not to worry, but you are definitely not alone!