Bill Cosby -- Accuser Thinks He May Have Confessed to Sexual Assault

Bill Cosby may have admitted under oath to sexually assaulting women ... at least that's what one alleged victim believes and is now trying to unearth documents to prove it.

Tamara Green claims Cosby drugged and groped her back in the '70s. The statute of limitations has long since run, but Green sued Cosby last December for defamation because he repeatedly said she was lying -- that it never happened.

Green has filed new legal docs -- obtained by TMZ -- in which she is trying to force Cosby to release his deposition in a lawsuit filed by another accuser -- Andrea Constand. She sued Cosby in 2005 and the case settled. The docs were all sealed.

Green believes Cosby may have admitted in his deposition to sexually assaulting other women, including Green herself.

We reached out to Cosby's rep ... so far no comment.