Archwires are changed when the current wire has achieved the tooth movements expected of it. For example, the thin, soft, round archwires used at the start are for lining the teeth up in a row and straightening out irregularities. Rectangular archwires work on the tilt of the teeth. If the round archwire currently in your mouth hasn't yet corrected the rotation of a particular tooth, it may be left to work for another month.
This answer is for general information. Your own case needs an examination by an orthodontist.