These days the police, cps and courts are getting strict with'domestic violance'.Even if your girlfriend has dropped the charges,the CPS can still prosecute if they feel that they still have a case.If there were any witnesses to whatever happened this will not got in your favour.My fiance is on a ABH charge for assaulting me.Even tho I am not pressing charges they have 2 independant witnesses.You do not say exactly what happened,or if it is your 1st offence or not.However,as much as I wish you the best of luck,I would strongly advise you to look at your actions which got you into this mess in the first place.