Feeling Sick After Reducing The Dose Of Metoprolol And Coreg After Heart Surgery. Which Medication Can Be Taken?

I take Benicar for high blood pressure, I was in the hospital 3 weeks ago with Walking Pneumonia, I have had open heart surgery, had 3 heart tests while there everything was good heart Dr put me on25 mg of Metoprolol. I have been sick everyday since Reg Dr told me to cut it in half, still the same , called heart Dr said he would put me on Coreg I see same side effects what other good is this as my blood pressure is fine before I even started this. I also have COPD which neither will help. Thanks