First off, well done in your recovery. One year of recovery is a great start to a lifetime without the need for drugs and alcohol.
My yoga teacher once had a theory that we yawn because we need more oxygen because we're breathing shallow breaths. Try some deep breathing once a day --- this is actually a good start toward meditation. The key is to teach yourself how to breathe deeply and re-program your body to do this more often.
Would you like me to post some resources?