What will stop me coughing?

Please help! I have a terrible cough, the dr has prescribed amoxycillin but so far after 4 days I am still coughing non stop, I can't eat or sleep properly & it is really getting me down! I am sleeping almost upright, but I am still waking up all night :( kovonia, benylin, codine linctus, etc have all failed to help.... I am hoping one of you guys can!!!