Was on 200mg of metoprolol now down to 25mg in the last 6 months due to bp dropping. what else would cause a 20 point drop in bp over the course of 3 weeks. had major surgery 5 weeks ago and bp has steadily dropped since then?

The worry and stress before the surgery could have been a component in your high BP prior to the surgery. Also, if you had a lot of pain before the surgery, this can cause your BP to be very elevated. I am not able to give you a complete answer since I do not know all your medical issues. Perhaps your doctor can give you an explanation as well.