Dear Anjana,
I am happy to hear that you and your dear brother are doing well! No, I do not think that gastrointestinal issues are a normal result of kidney donation.
Why don't you make an appointment with a gastroenterologist? GERD or another gastroenterological problem can cause fatigue.
Donating a kidney does not proof us against future health issues, nor can we assume that all future health issues are a result of the donation.
In any event, seeking professional medical care would be a good idea.
Love, elephant