Taking tylenol (acetaminophen) with codeine. Changed pharmacy. Suppose to be exact brand and dose. Makes me feel dizzy and tired. Same drug. How could this be?

Generic drugs. Generic drugs contain the same medication but are "build" with different components. Reabsorption and intolerance to the added non-medication part of the pill can make you feel different. Check on the maker of the initial brand you tolerated. You can call different pharmacies and see who carries the manufacturer.
Many possibilities. "suppose to be" is not same as "exact same" if you get my drift. Generics can vary from brands & each other by 10% or so more or less. So that might cause your dizziness & feeling tired. Or you might have another concurrent condition going on. Check w/pharmacy to be sure you're getting same thing. Then check w/family doc to be sure nothing else going on.