From Drugs.com:

"Wellbutrin XL is an extended release tablet which releases more slowly than the Wellbutrin SR tablet which is released faster. Another difference is that Wellbutrin SR is only used for major depressive disorder (MDD), whereas Wellbutrin XL can be used for both MDD and seasonal affective disorder (SAD)."

Maybe it you try XL, it will be gentler on your system thanks to slow continuous release and you will be spared spikes of anxiety. But this will require first seeing your psychiatrist.