Domestic Assault(Erwin,TN)?

Hello my name is Nathaniel Effler I'm writing in regards to a legal situation which I've found myself in.I was arrested and charged with Domestic Assault.I never hit her,there were no marks,bruises or black eyes.She told the officer that the situation was fine. She also informed the officer that she was NOT going to press charges.So instead the officer did.For some reason the D.A wants the pick up the case.There is no evidence what so ever.And the victim is my fiance.I'm also a convicted felon.This is what creates the problem.But i know the sate could not win in trial.PLEASE HELP