After cesarean hysterectomy and prolonged it has taken me months, and I still cannot stand long. What went wrong?

Probably nothing. A cesarean hysterectomy is major surgery. Some docs only perform this a handful of times during their career. The procedure implies that you completed a pregnancy, probably had a complication such as heavy bleeding and needed a life saving emergency surgery. It takes time to recover from each of these let alone all together. It may take months for your stamina to return. Follow up with the surgeon.